title: ngGrid afterSelectionChange not firing
body: <p>I have my ngGrid in a partial page, and I'm trying to access the selected items on the main page, I assume the best way to get this done is with $emit(to parent scope) and $on (to catch the event). For some reason my afterSelectionChange doesn't appear to be firing and I'm wondering if I'm just doing something wrong.  Or if there's a better way to track changes to a child grid selection even.</p>
  
  <p>I have
          <pre>{{mySelectedItems}}</pre>
  On my partial, and it updates just fine.  But also have 
          <pre>{{selectedDevices}}</pre>
  On my main view, and it's never getting updated.
  A breakpoint on the function within the "afterSelectionChange" also is not getting hit. here's the gridoptions.  zz is just my previously defined data, not really relevant, also chopped out my columnDefs to minimize space.</p>
  
  <pre><code>$scope.mySelectedItems = [];
  $scope.gridItems = @Html.Raw(Json.Encode(zz))
   $scope.gridOptions = {
      selectedItems:$scope.mySelectedItems,
      afterSelectionChange: function (data) {
          $scope.$emit("selectionChanged", $scope.mySelectedItems)},
      multiSelect:true,
      data: 'gridItems',
  enableColumnResize: true
  };
  </code></pre>
  
  <p>And finally on my main View, I have</p>
  
  <pre><code>$scope.$on("selectionChanged",function(event,data){
      $scope.selectedDevices=data;
  })
  </code></pre>
  
  <p>to catch the changes.</p>