title: Element not removed from collection with .splice(index, 1)
body: <p>I have a <code>$scope.inventories</code> that contains inventories I can select.
  I want to remove the selected item from <code>inventories</code> when something is selected, but that does not happen.</p>
  
  <p>Here is the code:</p>
  
  <pre><code>  $scope.select = (inventory, index) -&gt;
      url          = '/tasks/select_inventory'
      inventory_id = inventory.id
      $http(
        method: 'POST'
        url: url
        params: { task_id: task_id, inventory_id: inventory_id }
      ).success((data, status) -&gt;
        $scope.selected_inventories.push inventory
        $scope.inventories.splice(index, 1)
        return true
      ).error (data, status) -&gt;
        alert('failed')
        return
  </code></pre>
  
  <p><strong>The inventory model</strong></p>
  
  <pre><code>angular.module('orwapp').factory 'Inventory', ['$resource', ($resource) -&gt;
  
    Inventory = $resource "/api/v1/inventories/:id",
                        { id: "@id" }
  
    return Inventory
  ]
  </code></pre>
  
  <p>The Rails API returns <code>@task</code> as json. Is that OK?
  <code>render json: @task</code></p>
  
  <p>Why does not <code>$scope.inventories.splice(index, 1)</code> work as expected?</p>