title: UIRefreshControl How to detect if a user begins to drag down?
body: <p>I have a <code>UIRefreshControl</code> in a <code>UITableViewController</code>. Is there any way I can detect if a user begins to drag the View down to refresh the content? 
  I do not mean the <code>beginRefreshing</code> method. I want to be able to detect when a user begins to drag down - like when the circle fills up before the <code>beginRefreshing</code> method is called. Is this possible?</p>