Attach precipitating bufferChange to DisplayBuffer change events

The gutter can use this to determine if the change might have altered line numbers, for example if it's inside a fold.

src/app/display-buffer.coffee

@@ -207,7 +207,7 @@ class DisplayBuffer
     @trigger 'change',
       oldRange: oldScreenRange
       newRange: newScreenRange
-      bufferChanged: true
+      bufferChange: e.bufferChange
       lineNumbersChanged: !e.oldRange.coversSameRows(newRange) or !oldScreenRange.coversSameRows(newScreenRange)
 
   buildLineForBufferRow: (bufferRow) ->

src/app/edit-session.coffee

@@ -61,7 +61,7 @@ class EditSession
 
     @displayBuffer.on "change.edit-session-#{@id}", (e) =>
       @trigger 'screen-lines-change', e
-      unless e.bufferChanged
+      unless e.bufferChange
         anchor.refreshScreenPosition() for anchor in @getAnchors()
 
   destroy: ->

src/app/selection.coffee

@@ -13,7 +13,7 @@ class Selection
     @cursor.selection = this
 
     @cursor.on 'change-screen-position.selection', (e) =>
-      @screenRangeChanged() unless e.bufferChanged
+      @screenRangeChanged() unless e.bufferChange
 
     @cursor.on 'destroy.selection', =>
       @cursor = null