Use DeserializerManager::add disposable instead of ::remove in specs

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", ->

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", ->

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", ->