title: how to update filtered list view by binding filterProperty to certain value
body: <p>I have a list which based on certain properties returns a sub list. Is it possible to bind this property with outside control, so when it is set, the filtered list view can refresh itself.</p>
  
  <p>Right now if I do:</p>
  
  <p><code>MyApp.widgetIconsController.set 'iconareacolor', 'lightBlue'</code></p>
  
  <p>the filtered list didn't change  </p>
  
  <pre><code>{{#each MyApp.widgetIconsController.filtered}} 
      {{#view MyApp.IconView txtBinding ="this"}}
        &lt;div&gt; {{unbound txt.widgetName}} &lt;/div&gt;
      {{/view}}
   {{/each}} 
  
  MyApp.widgetIconsController = Ember.ArrayProxy.create
    iconareacolor: null
  
    content: [
      MyApp.ButtonWidget.create({'theme': 'lightblue'}),
      MyApp.TextWidget.create({'theme': 'lightblue'}),
      MyApp.ButtonWidget.create({'theme': 'lightcoral'}),
      MyApp.TextWidget.create({'theme': 'lightcoral'}),
      MyApp.InputWidget.create({'theme': 'lightcoral'}) ]
  
    filtered: (-&gt;
      filteredList = this.get("content").filterProperty 'theme', this.get('iconareacolor')
    ).property("content.@each.theme").cacheable()
  </code></pre>