title: Unable to extend DS.Model from ember-data
body: <p>This is my model</p>
  
  <pre><code>App.Person = DS.Model.extend({
      first_name: null,
      last_name: null,
      gender: null,
      profession: null,
      age: null
  });
  </code></pre>
  
  <p>And Firebug gives me 2 errors:</p>
  
  <pre><code>TypeError: Ember.EnumerableUtils is undefined
  [Break On This Error]   
  
  removeObject = Ember.EnumerableUtils.removeObject;
  </code></pre>
  
  <p>And this for Extending the DS.Model</p>
  
  <pre><code>TypeError: DS.Model is undefined
  [Break On This Error]   
  
  App.Person2 = DS.Model.extend({
  </code></pre>
  
  <p>Extending Ember.Object works fine with the same Model, i just can not use DS.*</p>
  
  <p>Google had 0 results for those error messages</p>