title: How to remove a UITabBarItem
body: <p>I have a nib with four UIViewControllers each with a UITabBarItem.  At runtime, based on user options, I need to show or hide one of the UITabBarItems.  I cannot figure out how to remove the UITabBatItem.</p>
  
  <p>Does anyone know how to do this?</p>
  
  <p>Thanks</p>