title: UITableView pull to refresh automatically
body: <p>I got a <code>UITableViewController</code> and the data of the list is get from the server.
  Supporting scroll down to refresh data.</p>
  
  <p>My question is when view did load. I don't want user use finger to pull it down get the data, but <code>UITableView</code> scroll down itself automatically and get data from server.</p>
  
  <p><strong>Edit:</strong></p>
  
  <p>Sorry, my question is there is a method named <code>pullDownToRefresh</code>, for example. If user use finger to pull down the <code>tableView</code>, the function is triggered. And now, I want to make <code>tableview</code> pull down by itself, and trigger the function automatically. </p>
  
  <p>I also need to make <code>tableView</code> scrolls down. I tried <code>beginRefreshing</code>, but the <code>tableView</code> is not really scrolls down.</p>