title: External Filter on ag-grid not working
body: <p>I don't want to use the built-in Filter on ag-grid, so I tried using External Filtering in ag-grid, without success. Can someone steer me in the right direction?</p>
  
  <p><strong>HTML:</strong></p>
  
  <pre><code>&lt;input class="ag-filter-filter" id="filterText" type="text" ng-   change="filterOwnerField()" ng-model="Owner" placeholder="Filter Owner" /&gt;
  </code></pre>
  
  <p><strong>AngularJS:</strong></p>
  
  <pre><code>function isExternalFilterPresent()
  {
      return $scope.Owner != '';
  }
  
  function doesExternalFilterPass()
  {
      return $scope.Owner != '';
  }
  
  $scope.filterOwnerField = function ()
  {
      $scope.gridOptions.api.onFilterChanged();
  };
  </code></pre>