Add editor.showLineNumbers config option

Also adds toggle-line-numbers command. Closes #377

spec/app/editor-spec.coffee

@@ -1707,6 +1707,12 @@ describe "Editor", ->
         miniEditor.setText(" a line with tabs\tand spaces ")
         expect(miniEditor.renderedLines.find('.line').text()).toBe "#{space}a line with tabs#{tab} and spaces#{space}"
 
+    describe "when config.editor.showLineNumbers is false", ->
+      it "doesn't render any line numbers", ->
+        expect(editor.gutter.lineNumbers).toBeVisible()
+        config.set("editor.showLineNumbers", false)
+        expect(editor.gutter.lineNumbers).not.toBeVisible()
+
   describe "gutter line highlighting", ->
     beforeEach ->
       editor.attachToDom(heightInLines: 5.5)

src/app/editor.coffee

@@ -16,6 +16,7 @@ class Editor extends View
     fontSize: 20
     showInvisibles: false
     showIndentGuide: false
+    showLineNumbers: true
     autoIndent: true
     autoIndentOnPaste: false
     nonWordCharacters: "./\\()\"':,.;<>~!@#$%^&*|+=[]{}`~?-"
@@ -156,6 +157,7 @@ class Editor extends View
         'editor:duplicate-line': @duplicateLine
         'editor:toggle-indent-guide': => config.set('editor.showIndentGuide', !config.get('editor.showIndentGuide'))
         'editor:save-debug-snapshot': @saveDebugSnapshot
+        'editor:toggle-line-numbers': =>  config.set('editor.showLineNumbers', !config.get('editor.showLineNumbers'))
 
     documentation = {}
     for name, method of editorBindings
@@ -316,6 +318,7 @@ class Editor extends View
   backwardsScanInRange: (args...) -> @getBuffer().backwardsScanInRange(args...)
 
   configure: ->
+    @observeConfig 'editor.showLineNumbers', (showLineNumbers) => @gutter.setShowLineNumbers(showLineNumbers)
     @observeConfig 'editor.showInvisibles', (showInvisibles) => @setShowInvisibles(showInvisibles)
     @observeConfig 'editor.showIndentGuide', (showIndentGuide) => @setShowIndentGuide(showIndentGuide)
     @observeConfig 'editor.invisibles', (invisibles) => @setInvisibles(invisibles)

src/app/gutter.coffee

@@ -24,6 +24,9 @@ class Gutter extends View
   editor: ->
     @parentView
 
+  setShowLineNumbers: (showLineNumbers) ->
+    if showLineNumbers then @lineNumbers.show() else @lineNumbers.hide()
+
   updateLineNumbers: (changes, renderFrom, renderTo) ->
     if renderFrom < @firstScreenRow or renderTo > @lastScreenRow
       performUpdate = true