title: Ember-data: How DS.attr("number") is supposed to work?
body: <p>I'm using DS.RESTAdapter, php on server. I have a model UacList:</p>
  
  <pre><code>DS.Model.extend({
      dummyFieldForErrors: DS.attr("string"),
      selected: DS.attr("number"),
      uacs: DS.hasMany("uac")
  });
  </code></pre>
  
  <p>Ember sends request GET /rest/uacLists/1. Server response is:</p>
  
  <pre><code>{
      "uacList":{
          "id":1,
          "selected":32483,
          "uacs":[33618,9678,...,33656]
      },
      "uacs": [...]
  }
  </code></pre>
  
  <p>But Ember Inspector tells me that selected is undefined (other attributes have values they should have according to server response). No matter if there is a quotes ("selected":"32483") or not ("selected":32483), it is undefined anyway. If I define this attribute as a string, it works but I don't like when an integer is defined as a string.</p>