title: UIRefreshControl - beginRefreshing not working when UITableViewController is inside UINavigationController
body: <p>I've setup a UIRefreshControl in my UITableViewController (which is inside a UINavigationController) and it works as expected (i.e. pull down fires the correct event). However, if I programmatically invoke the <code>beginRefreshing</code> instance method on the refresh control like:</p>
  
  <pre><code>[self.refreshControl beginRefreshing];
  </code></pre>
  
  <p>Nothing happens. It should animate down and show the spinner. The <code>endRefreshing</code> method works properly when I call that after the refresh.</p>
  
  <p>I whipped up a basic prototype project with this behavior and it works properly when my UITableViewController is added directly to application delegate's root view controller, e.g:</p>
  
  <pre><code>self.viewController = tableViewController;
  self.window.rootViewController = self.viewController;
  </code></pre>
  
  <p>But if I add the <code>tableViewController</code> to a UINavigationController first, then add the navigation controller as the <code>rootViewController</code>, the <code>beginRefreshing</code> method no longer works. E.g.</p>
  
  <pre><code>UINavigationController *navController = [[UINavigationController alloc] initWithRootViewController:tableViewController];
  self.viewController = navController;
  self.window.rootViewController = self.viewController;
  </code></pre>
  
  <p>My feeling is this has something to do with the nested view hierarchies within the navigation controller not playing nice with the refresher control - any suggestions?</p>
  
  <p>Thanks </p>