diff --git a/coffeelint.json b/coffeelint.json
index 9535d90ac..d8e19fc46 100644
--- a/coffeelint.json
+++ b/coffeelint.json
@@ -10,5 +10,8 @@
   },
   "no_interpolation_in_single_quotes": {
     "level": "error"
+  },
+  "no_debugger": {
+    "level": "error"
   }
 }
diff --git a/package.json b/package.json
index bf7c1be48..4f5babcbd 100644
--- a/package.json
+++ b/package.json
@@ -1,7 +1,7 @@
 {
   "name": "atom",
   "productName": "Atom",
-  "version": "0.133.0",
+  "version": "0.134.0",
   "description": "A hackable text editor for the 21st Century.",
   "main": "./src/browser/main.js",
   "repository": {
@@ -20,7 +20,7 @@
   "atomShellVersion": "0.16.2",
   "dependencies": {
     "async": "0.2.6",
-    "atom-keymap": "^2.1.3",
+    "atom-keymap": "^2.2.0",
     "bootstrap": "git+https://github.com/atom/bootstrap.git#6af81906189f1747fd6c93479e3d998ebe041372",
     "clear-cut": "0.4.0",
     "coffee-script": "1.7.0",
@@ -28,7 +28,7 @@
     "delegato": "^1",
     "emissary": "^1.3.1",
     "event-kit": "0.7.2",
-    "first-mate": "^2.1.2",
+    "first-mate": "^2.2.0",
     "fs-plus": "^2.2.6",
     "fstream": "0.1.24",
     "fuzzaldrin": "^2.1",
@@ -97,7 +97,7 @@
     "open-on-github": "0.30.0",
     "package-generator": "0.31.0",
     "release-notes": "0.36.0",
-    "settings-view": "0.147.0",
+    "settings-view": "0.148.0",
     "snippets": "0.53.0",
     "spell-check": "0.42.0",
     "status-bar": "0.45.0",
diff --git a/spec/config-spec.coffee b/spec/config-spec.coffee
index 450564ea2..666c76b3d 100644
--- a/spec/config-spec.coffee
+++ b/spec/config-spec.coffee
@@ -426,6 +426,7 @@ describe "Config", ->
     updatedHandler = null
 
     beforeEach ->
+      atom.config.setDefaults('foo', bar: 'def')
       atom.config.configDirPath = dotAtomPath
       atom.config.configFilePath = path.join(atom.config.configDirPath, "atom.config.cson")
       expect(fs.existsSync(atom.config.configDirPath)).toBeFalsy()
@@ -447,6 +448,34 @@ describe "Config", ->
           expect(atom.config.get('foo.bar')).toBe 'quux'
           expect(atom.config.get('foo.baz')).toBe 'bar'
 
+    describe "when the config file changes to omit a setting with a default", ->
+      it "resets the setting back to the default", ->
+        fs.writeFileSync(atom.config.configFilePath, "foo: { baz: 'new'}")
+        waitsFor 'update event', -> updatedHandler.callCount > 0
+        runs ->
+          expect(atom.config.get('foo.bar')).toBe 'def'
+          expect(atom.config.get('foo.baz')).toBe 'new'
+
+    describe "when the config file changes to be empty", ->
+      beforeEach ->
+        fs.writeFileSync(atom.config.configFilePath, "")
+        waitsFor 'update event', -> updatedHandler.callCount > 0
+
+      it "resets all settings back to the defaults", ->
+        expect(updatedHandler.callCount).toBe 1
+        expect(atom.config.get('foo.bar')).toBe 'def'
+        atom.config.set("hair", "blonde") # trigger a save
+        expect(atom.config.save).toHaveBeenCalled()
+
+      describe "when the config file subsequently changes again to contain configuration", ->
+        beforeEach ->
+          updatedHandler.reset()
+          fs.writeFileSync(atom.config.configFilePath, "foo: bar: 'newVal'")
+          waitsFor 'update event', -> updatedHandler.callCount > 0
+
+        it "sets the setting to the value specified in the config file", ->
+          expect(atom.config.get('foo.bar')).toBe 'newVal'
+
     describe "when the config file changes to contain invalid cson", ->
       beforeEach ->
         spyOn(console, 'error')
diff --git a/spec/deserializer-manager-spec.coffee b/spec/deserializer-manager-spec.coffee
index 3a2bf95e4..15c8a2648 100644
--- a/spec/deserializer-manager-spec.coffee
+++ b/spec/deserializer-manager-spec.coffee
@@ -1,33 +1,44 @@
 DeserializerManager = require '../src/deserializer-manager'
 
-describe ".deserialize(state)", ->
-  deserializer = null
+describe "DeserializerManager", ->
+  manager = null
 
   class Foo
     @deserialize: ({name}) -> new Foo(name)
     constructor: (@name) ->
 
   beforeEach ->
-    deserializer = new DeserializerManager()
-    deserializer.add(Foo)
+    manager = new DeserializerManager
 
-  it "calls deserialize on the deserializer for the given state object, or returns undefined if one can't be found", ->
-    spyOn(console, 'warn')
-    object = deserializer.deserialize({ deserializer: 'Foo', name: 'Bar' })
-    expect(object.name).toBe 'Bar'
-    expect(deserializer.deserialize({ deserializer: 'Bogus' })).toBeUndefined()
+  describe "::add(deserializer)", ->
+    it "returns a disposable that can be used to remove the manager", ->
+      disposable = manager.add(Foo)
+      expect(manager.deserialize({deserializer: 'Foo', name: 'Bar'})).toBeDefined()
+      disposable.dispose()
+      spyOn(console, 'warn')
+      expect(manager.deserialize({deserializer: 'Foo', name: 'Bar'})).toBeUndefined()
 
-  describe "when the deserializer has a version", ->
+  describe "::deserialize(state)", ->
     beforeEach ->
-      Foo.version = 2
+      manager.add(Foo)
 
-    describe "when the deserialized state has a matching version", ->
-      it "attempts to deserialize the state", ->
-        object = deserializer.deserialize({ deserializer: 'Foo', version: 2, name: 'Bar' })
-        expect(object.name).toBe 'Bar'
+    it "calls deserialize on the manager for the given state object, or returns undefined if one can't be found", ->
+      spyOn(console, 'warn')
+      object = manager.deserialize({deserializer: 'Foo', name: 'Bar'})
+      expect(object.name).toBe 'Bar'
+      expect(manager.deserialize({deserializer: 'Bogus'})).toBeUndefined()
 
-    describe "when the deserialized state has a non-matching version", ->
-      it "returns undefined", ->
-        expect(deserializer.deserialize({ deserializer: 'Foo', version: 3, name: 'Bar' })).toBeUndefined()
-        expect(deserializer.deserialize({ deserializer: 'Foo', version: 1, name: 'Bar' })).toBeUndefined()
-        expect(deserializer.deserialize({ deserializer: 'Foo', name: 'Bar' })).toBeUndefined()
+    describe "when the manager has a version", ->
+      beforeEach ->
+        Foo.version = 2
+
+      describe "when the deserialized state has a matching version", ->
+        it "attempts to deserialize the state", ->
+          object = manager.deserialize({deserializer: 'Foo', version: 2, name: 'Bar'})
+          expect(object.name).toBe 'Bar'
+
+      describe "when the deserialized state has a non-matching version", ->
+        it "returns undefined", ->
+          expect(manager.deserialize({deserializer: 'Foo', version: 3, name: 'Bar'})).toBeUndefined()
+          expect(manager.deserialize({deserializer: 'Foo', version: 1, name: 'Bar'})).toBeUndefined()
+          expect(manager.deserialize({deserializer: 'Foo', name: 'Bar'})).toBeUndefined()
diff --git a/spec/pane-container-view-spec.coffee b/spec/pane-container-view-spec.coffee
index 8bbb75243..a48269a1a 100644
--- a/spec/pane-container-view-spec.coffee
+++ b/spec/pane-container-view-spec.coffee
@@ -5,11 +5,11 @@ PaneView = require '../src/pane-view'
 {$, View, $$} = require 'atom'
 
 describe "PaneContainerView", ->
-  [TestView, container, pane1, pane2, pane3] = []
+  [TestView, container, pane1, pane2, pane3, deserializerDisposable] = []
 
   beforeEach ->
     class TestView extends View
-      atom.deserializers.add(this)
+      deserializerDisposable = atom.deserializers.add(this)
       @deserialize: ({name}) -> new TestView(name)
       @content: -> @div tabindex: -1
       initialize: (@name) -> @text(@name)
@@ -25,7 +25,7 @@ describe "PaneContainerView", ->
     pane3 = pane2.splitDown(new TestView('3'))
 
   afterEach ->
-    atom.deserializers.remove(TestView)
+    deserializerDisposable.dispose()
 
   describe ".getActivePaneView()", ->
     it "returns the most-recently focused pane", ->
diff --git a/spec/pane-spec.coffee b/spec/pane-spec.coffee
index 01dcda025..748de6c36 100644
--- a/spec/pane-spec.coffee
+++ b/spec/pane-spec.coffee
@@ -4,6 +4,8 @@ PaneAxis = require '../src/pane-axis'
 PaneContainer = require '../src/pane-container'
 
 describe "Pane", ->
+  deserializerDisposable = null
+
   class Item extends Model
     @deserialize: ({name, uri}) -> new this(name, uri)
     constructor: (@name, @uri) ->
@@ -13,10 +15,10 @@ describe "Pane", ->
     isEqual: (other) -> @name is other?.name
 
   beforeEach ->
-    atom.deserializers.add(Item)
+    deserializerDisposable = atom.deserializers.add(Item)
 
   afterEach ->
-    atom.deserializers.remove(Item)
+    deserializerDisposable.dispose()
 
   describe "construction", ->
     it "sets the active item to the first item", ->
diff --git a/spec/pane-view-spec.coffee b/spec/pane-view-spec.coffee
index 2a92ff3d5..5aa8c4ffc 100644
--- a/spec/pane-view-spec.coffee
+++ b/spec/pane-view-spec.coffee
@@ -7,7 +7,7 @@ path = require 'path'
 temp = require 'temp'
 
 describe "PaneView", ->
-  [container, containerModel, view1, view2, editor1, editor2, pane, paneModel] = []
+  [container, containerModel, view1, view2, editor1, editor2, pane, paneModel, deserializerDisposable] = []
 
   class TestView extends View
     @deserialize: ({id, text}) -> new TestView({id, text})
@@ -23,7 +23,7 @@ describe "PaneView", ->
       @emitter.on 'did-change-title', callback
 
   beforeEach ->
-    atom.deserializers.add(TestView)
+    deserializerDisposable = atom.deserializers.add(TestView)
     container = new PaneContainerView
     containerModel = container.model
     view1 = new TestView(id: 'view-1', text: 'View 1')
@@ -40,7 +40,7 @@ describe "PaneView", ->
       paneModel.addItems([view1, editor1, view2, editor2])
 
   afterEach ->
-    atom.deserializers.remove(TestView)
+    deserializerDisposable.dispose()
 
   describe "when the active pane item changes", ->
     it "hides all item views except the active one", ->
diff --git a/spec/theme-manager-spec.coffee b/spec/theme-manager-spec.coffee
index 4a037d2f9..c7b64fec2 100644
--- a/spec/theme-manager-spec.coffee
+++ b/spec/theme-manager-spec.coffee
@@ -52,7 +52,7 @@ describe "ThemeManager", ->
 
       expect(themeManager.getEnabledThemeNames()).toEqual ['atom-dark-ui', 'atom-light-ui']
 
-  describe "getImportPaths()", ->
+  describe "::getImportPaths()", ->
     it "returns the theme directories before the themes are loaded", ->
       atom.config.set('core.themes', ['theme-with-index-less', 'atom-dark-ui', 'atom-light-ui'])
 
@@ -129,7 +129,7 @@ describe "ThemeManager", ->
       spyOn(console, 'warn')
       expect(-> atom.packages.activatePackage('a-theme-that-will-not-be-found')).toThrow()
 
-  describe "requireStylesheet(path)", ->
+  describe "::requireStylesheet(path)", ->
     it "synchronously loads css at the given path and installs a style tag for it in the head", ->
       themeManager.onDidChangeStylesheets stylesheetsChangedHandler = jasmine.createSpy("stylesheetsChangedHandler")
       themeManager.onDidAddStylesheet stylesheetAddedHandler = jasmine.createSpy("stylesheetAddedHandler")
@@ -185,18 +185,17 @@ describe "ThemeManager", ->
       $('head style[id*="css.css"]').remove()
       $('head style[id*="sample.less"]').remove()
 
-  describe ".removeStylesheet(path)", ->
-    it "removes styling applied by given stylesheet path", ->
+    it "returns a disposable allowing styles applied by the given path to be removed", ->
       cssPath = require.resolve('./fixtures/css.css')
 
       expect($(document.body).css('font-weight')).not.toBe("bold")
-      themeManager.requireStylesheet(cssPath)
+      disposable = themeManager.requireStylesheet(cssPath)
       expect($(document.body).css('font-weight')).toBe("bold")
 
       themeManager.onDidRemoveStylesheet stylesheetRemovedHandler = jasmine.createSpy("stylesheetRemovedHandler")
       themeManager.onDidChangeStylesheets stylesheetsChangedHandler = jasmine.createSpy("stylesheetsChangedHandler")
 
-      themeManager.removeStylesheet(cssPath)
+      disposable.dispose()
 
       expect($(document.body).css('font-weight')).not.toBe("bold")
 
diff --git a/src/config.coffee b/src/config.coffee
index b2eb74f1e..f2063cdf1 100644
--- a/src/config.coffee
+++ b/src/config.coffee
@@ -533,7 +533,11 @@ class Config
 
     try
       userConfig = CSON.readFileSync(@configFilePath)
-      @setRecursive(null, userConfig)
+      @settings = {} # Reset to the defaults
+      if isPlainObject(userConfig)
+        @setRecursive(null, userConfig)
+      else
+        @emitter.emit 'did-change'
       @configFileHasErrors = false
     catch error
       @configFileHasErrors = true
diff --git a/src/deserializer-manager.coffee b/src/deserializer-manager.coffee
index 9abefc4c6..50becb31a 100644
--- a/src/deserializer-manager.coffee
+++ b/src/deserializer-manager.coffee
@@ -1,3 +1,6 @@
+{Disposable} = require 'event-kit'
+Grim = require 'grim'
+
 # Extended: Manages the deserializers used for serialized state
 #
 # An instance of this class is always available as the `atom.deserializers`
@@ -24,14 +27,17 @@ class DeserializerManager
 
   # Public: Register the given class(es) as deserializers.
   #
-  # * `classes` One or more classes to register.
-  add: (classes...) ->
-    @deserializers[klass.name] = klass for klass in classes
+  # * `deserializers` One or more deserializers to register. A deserializer can
+  #   be any object with a `.name` property and a `.deserialize()` method. A
+  #   common approach is to register a *constructor* as the deserializer for its
+  #   instances by adding a `.deserialize()` class method.
+  add: (deserializers...) ->
+    @deserializers[deserializer.name] = deserializer for deserializer in deserializers
+    new Disposable =>
+      delete @deserializers[deserializer.name] for deserializer in deserializers
 
-  # Public: Remove the given class(es) as deserializers.
-  #
-  # * `classes` One or more classes to remove.
   remove: (classes...) ->
+    Grim.deprecate("Call .dispose() on the Disposable return from ::add instead")
     delete @deserializers[name] for {name} in classes
 
   # Public: Deserialize the state and params.
diff --git a/src/theme-manager.coffee b/src/theme-manager.coffee
index 1aebe757b..9ea248a26 100644
--- a/src/theme-manager.coffee
+++ b/src/theme-manager.coffee
@@ -2,7 +2,7 @@ path = require 'path'
 
 _ = require 'underscore-plus'
 EmitterMixin = require('emissary').Emitter
-{Emitter} = require 'event-kit'
+{Emitter, Disposable} = require 'event-kit'
 {File} = require 'pathwatcher'
 fs = require 'fs-plus'
 Q = require 'q'
@@ -182,16 +182,16 @@ class ThemeManager
   # * `stylesheetPath` A {String} path to the stylesheet that can be an absolute
   #   path or a relative path that will be resolved against the load path.
   #
-  # Returns the absolute path to the required stylesheet.
+  # Returns a {Disposable} on which `.dispose()` can be called to remove the
+  # required stylesheet.
   requireStylesheet: (stylesheetPath, type='bundled') ->
     if fullPath = @resolveStylesheet(stylesheetPath)
       content = @loadStylesheet(fullPath)
       @applyStylesheet(fullPath, content, type)
+      new Disposable => @removeStylesheet(fullPath)
     else
       throw new Error("Could not find a file at path '#{stylesheetPath}'")
 
-    fullPath
-
   unwatchUserStylesheet: ->
     @userStylesheetFile?.off()
     @userStylesheetFile = null
diff --git a/src/workspace.coffee b/src/workspace.coffee
index 65bf5895f..1d890c217 100644
--- a/src/workspace.coffee
+++ b/src/workspace.coffee
@@ -5,7 +5,8 @@ _ = require 'underscore-plus'
 Q = require 'q'
 Serializable = require 'serializable'
 Delegator = require 'delegato'
-{Emitter} = require 'event-kit'
+{Emitter, Disposable} = require 'event-kit'
+Grim = require 'grim'
 TextEditor = require './text-editor'
 PaneContainer = require './pane-container'
 Pane = require './pane'
@@ -363,11 +364,16 @@ class Workspace extends Model
   # ```
   #
   # * `opener` A {Function} to be called when a path is being opened.
+  #
+  # Returns a {Disposable} on which `.dispose()` can be called to remove the
+  # opener.
   registerOpener: (opener) ->
     @openers.push(opener)
+    new Disposable => _.remove(@openers, opener)
 
   # Unregister an opener registered with {::registerOpener}.
   unregisterOpener: (opener) ->
+    Grim.deprecate("Call .dispose() on the Disposable returned from ::registerOpener instead")
     _.remove(@openers, opener)
 
   getOpeners: ->