title: angularUI ui-grid grouping feature missing?
body: <p>I am using <code>angularUI</code>'s new directive (<a href="http://ui-grid.info/" rel="nofollow">uiGrid</a>) after they announced that it a replacement for the old one (<a href="http://angular-ui.github.io/ng-grid/" rel="nofollow">ngGrid</a>).</p>
  
  <p>it's pretty awesome but I can't find the <strong>grouping</strong> feature, although mentioned in their <a href="http://ui-grid.info/" rel="nofollow">home page</a> under <code>Advanced Features</code>.</p>
  
  <p>Am I missing something? Is there a way for me to have grouping feature in this component?</p>
  
  <p>thank you.</p>