title: Add attributes for UITableViewController
body: <p>I'm developing a custom class.
  The goal is user will add a <code>UITableViewController</code> to the storyboard and set its class to mine.
  and my class will fill the <code>tableView</code>.</p>
  
  <p>Here's my question: I want to give the user to set some attributes like header color, etc in storyboard, but <code>@IBdesignable</code> can't be used for <code>UITableViewController</code></p>
  
  <p>Any idea? </p>