title: Backbone.marionette compositeview ignores the index for addItemView
body: <p>I am using Backbone.Marionette's CompositeView and I want to insert a new model at index 0 of the collection and have it appear as the first view in the composite.</p>
  
  <p>I have this code to insert the element:</p>
  
  <pre><code>PlansApp.Plans.collection.unshift new PlansApp.Plan data
  </code></pre>
  
  <p>The problem is that the CompositeView ignores the index of the newly inserted item in the collection.</p>
  
  <p>in Backbone.Marionette, the appendHtml method looks like this:</p>
  
  <pre><code>  appendHtml: function(collectionView, itemView, index){
      collectionView.$el.append(itemView.el);
    },
  </code></pre>
  
  <p>The index argument is never used.</p>
  
  <p>The newly inserted view will always be placed at the end of the composite.</p>
  
  <p>How can I get it to appear at position 0?</p>