title: how to update model's object in each loop
body: <p>I tried to update each object in my model within a each loop</p>
  
  <p>I wanna add <code>size</code> property to each object in the model.</p>
  
  <p>But it seems doesn't work.</p>
  
  <h2>CONSOLE (it didn't work after I appended size property)</h2>
  
  <pre><code>self.model().get(i).size=123
  &gt;&gt; 123
  
  self.model().get(i)
  &gt;&gt;
  id: 1
  name: "URL_Command_Comparison"
  rounds: 2
  team: "cvt"
  __proto__: Object
  </code></pre>
  
  <h2>CODE</h2>
  
  <pre><code>  model: function(){
      return Ember.A([
        {id: 1, name: 'URL_Command_Comparison', 
          team: 'cvt'
        },
        {id: 2, name: 'Auto Test',
          'manualHours':20 ,'autoHours': 3, 
        ....
  $.each(this.model(),function(i,d){
    self.model().get(i).set("size",self.perRoundROI(d)*d.rounds*d.coverage)
  });
  </code></pre>