title: iOS tab bar item with no controller associated
body: <p>I have my own subclass of UITabBarController. I am trying now to add a simple button (UITabBarItem) in the storyboard. The thing is that I don't want to associate a controller with it. An action on that item will simply fire a prompting alert to confirm switching between two modes.</p>
  
  <p>So, what is the clean way to add an element in tab bar from StoryBoard without linking to anything (and doing stuff programatically) ?</p>