title: ngRepeat:dupes - Duplicates in a repeater are not allowed
body: <p>I am using ngTagsInput directive with auto-complete. Everything works fine if i dont have two tags with same "tag_token" property.</p>
  
  <p>This is my response that i get:</p>
  
  <pre><code>{
  "id": "100",
  "create_date": "2016-02-01T18:33:39Z",
  "tag_token": "Tag 1",
  "parent_id": "1",
  "parent_type": "FILE"
  },
  {
  "id": "101",
  "create_date": "2016-02-01T18:33:39Z",
  "tag_token": "Tag 2",
  "parent_id": "2",
  "parent_type": "FILE"
  },
  {
  "id": "102",
  "create_date_tdt": "2016-02-01T18:33:39Z",
  "tag_token": "Tag 2",
  "parent_id": "3",
  "parent_type": "FILE"
  }
  </code></pre>
  
  <p><strong>VIEW</strong></p>
  
  <pre><code>                 &lt;tags-input             
                      ng-model="searchQuery"
                      display-property="tag_token"
                      key-property="tag_token"
                      on-tag-adding="checkTag($tag)"
                      on-tag-removed="onTagRemoved($tag)"
                      replace-spaces-with-dashes="false"
                      add-from-autocomplete-only="true"
                  &gt;
                  &lt;auto-complete min-length="1" max-results-to-show="10" source="typeahead($query)"&gt;&lt;/auto-complete&gt;
                  &lt;/tags-input&gt;
  </code></pre>
  
  <p>I am getting this error:</p>
  
  <pre><code>Error: [ngRepeat:dupes] Duplicates in a repeater are not allowed. Use 'track by' expression to specify unique keys. Repeater: item in suggestionList.items track by track(item), Duplicate key: Tag 2, Duplicate value: {"tag_token":"Tag 2"}
  http://errors.angularjs......
      at angular.js:68
      at ngRepeatAction (angular.js:27518)
      at Object.$watchCollectionAction [as fn] (angular.js:15761)
      at Scope.$digest (angular.js:15896)
      at Scope.$apply (angular.js:16160)
      at done (angular.js:10589)
      at completeRequest (angular.js:10787)
      at XMLHttpRequest.requestLoaded (angular.js:10728)
  </code></pre>