presenter: use 'markers-updated' event for state updates

Signed-off-by: Nathan Sobo <nathan@github.com>

src/text-editor.coffee

@@ -163,10 +163,10 @@ class TextEditor extends Model
 
   subscribeToDisplayBuffer: ->
     @disposables.add @displayBuffer.onDidCreateMarker @handleMarkerCreated
-    @disposables.add @displayBuffer.onDidUpdateMarkers => @mergeIntersectingSelections()
     @disposables.add @displayBuffer.onDidChangeGrammar => @handleGrammarChange()
     @disposables.add @displayBuffer.onDidTokenize => @handleTokenization()
     @disposables.add @displayBuffer.onDidChange (e) =>
+      @mergeIntersectingSelections()
       @emit 'screen-lines-changed', e if includeDeprecatedAPIs
       @emitter.emit 'did-change', e
 
@@ -461,6 +461,9 @@ class TextEditor extends Model
   onDidChangeIcon: (callback) ->
     @emitter.on 'did-change-icon', callback
 
+  onDidUpdateMarkers: (callback) ->
+    @displayBuffer.onDidUpdateMarkers(callback)
+
   # Public: Retrieves the current {TextBuffer}.
   getBuffer: -> @buffer