title: angular material md-select using track by but still getting $$hashKey
body: <p>I'm trying to get rid of the $$hashKey value that angular adds to your model value. According to most sources implementing a track by should solve this issue but I'm doing something wrong.</p>
  
  <p>The vm.productTypes is any array of objects with id properties that are GUIDs.</p>
  
  <p>Resulting model value...</p>
  
  <pre><code>$$hashKey: "object:445"
  id: "9e695340-d10a-40ca-9cff-e9a93388912a"
  name: "Medical"
  type: 1
  typeString: "ProductTypes"
  </code></pre>
  
  <p>HTML Code :</p>
  
  <pre><code>&lt;md-select id="type" ng-model="vm.currentProduct.productType" name="type"
                             ng-model-options="{trackBy: '$value.id'}"
                             required&gt;
                      &lt;md-option ng-repeat="pt in vm.productTypes track by pt.id" ng-value="pt"&gt;
                          {{pt.name}}
                      &lt;/md-option&gt;
                  &lt;/md-select&gt;
  </code></pre>
  
  <p>Where am I going wrong?</p>
  
  <p><strong>Update:</strong></p>
  
  <p>Seems that the name attribute is causing this strange behavior. Bug? 
  <a href="http://codepen.io/anon/pen/LNpMYJ" rel="nofollow">http://codepen.io/anon/pen/LNpMYJ</a></p>