title: how to hide/show ng-grid column externally?
body: <p>I am using <code>ng-grid</code>  where i want to <strong>hide/show</strong> columns on external <em>button click</em>.</p>
  
  <p>I tried this, but its not working</p>
  
  <pre><code>$scope.gridOptions.$gridScope.columns[0].toggleVisible()
  </code></pre>