title: Angular 4 FormGroup removeControl() does not update the form
body: <p>I'm trying to figure out how to remove an element from a reactive form.</p>
  
  <p>Here's a plunker of a small example: <a href="http://plnkr.co/edit/HyhMDoMtek02CyKpZ7Wt?p=preview" rel="noreferrer">http://plnkr.co/edit/HyhMDoMtek02CyKpZ7Wt?p=preview</a></p>
  
  <p>When I hit the <code>X</code> button, the form object is updated but the form UI still has the item on there.</p>
  
  <p>How do I get the form to update itself on the remove?</p>