title: AngularJS | orderBy filter not updated dynamically
body: <p>I'm having trouble with the <code>orderBy</code> filter in AngularJS. Here's my setup:</p>
  
  <pre><code>&lt;li ng-repeat="item in listItems.data | orderBy:order"&gt;
      &lt;a ng-click="getRelated(item._id)"&gt;{{ item.title }}&lt;/a&gt;
  &lt;/li&gt;
  </code></pre>
  
  <p>Part of the controller:</p>
  
  <pre><code>$scope.order = 'year';
  
  $scope.listItems = $http.post($scope.url, {'filterType': 'abc', 'letter': $scope.params.letter});
  
  $scope.setOrder = function(order) {
      $scope.order = order;
  }
  </code></pre>
  
  <p>And finally the "switches" I would like to use for ordering the data</p>
  
  <pre><code>    &lt;span class="sort--title"&gt;Sort by&lt;/span&gt;
      &lt;a ng-class="{true:'selected', false:''}[order=='title']" href="" ng-click="setOrder('title')" class="sort--attribute"&gt;Title&lt;/a&gt;
      &lt;a ng-class="{true:'selected', false:''}[order=='year']" href="" ng-click="setOrder('year')" class="sort--attribute"&gt;Year&lt;/a&gt;
      &lt;a ng-class="{true:'selected', false:''}[order=='length']" href="" ng-click="setOrder('length')" class="sort--attribute"&gt;Length&lt;/a&gt;
      &lt;a ng-class="{true:'selected', false:''}[order=='date_added']" href="" ng-click="setOrder('date_added')" class="sort--attribute"&gt;Date Added&lt;/a&gt;
  </code></pre>
  
  <p>When I click the buttons, the list is not being re-ordered.
  <strong>When I manually change the initial <code>$scope.order</code> value, the list is ordered by the property. Also <code>ng-class</code> is updated correctly. I'm obviously missing out something!</strong></p>