title: Backbone collection fetch (add:true) does not update the collection
body: <pre><code>loadMore: function(){
      var $this = this;
      console.log(this.Messages); //SAME AS AFTER
      this.Messages.url = '/js/messages/?start=' + this.Messages.length
      this.Messages.fetch({'add':true,
          success:function(){
              console.log($this.Messages); //SAME AS BEFORE??
          },
          error:function(){
          }
      });
   },
  </code></pre>
  
  <p>The collection is not updated. After this function, the events are fired, and the new items are drawn on the screen.  The problem is that the collection did not add the new models.</p>