Update richmarker.js to send marker as argument to 'dragend' callback

Unless the marker object is sent as an argument in the callback, you can only use anonymous functions which have the marker in scope.

src/richmarker.js

@@ -526,7 +526,7 @@ RichMarker.prototype.stopDrag = function() {
     this.removeDraggingListeners_();
 
     this.setCursor_('draggable');
-    google.maps.event.trigger(this, 'dragend');
+    google.maps.event.trigger(this, 'dragend', this);
 
     this.draw();
   }