title: Set rootViewController of UINavigationController by method other than initWithRootViewController
body: <p>How Do I set the <code>rootViewController</code> of <code>UINavigationController</code> by a method other than <code>initWithRootViewController</code>?</p>
  
  <p>I want use <code>initWithNavigationBarClass:toolbarClass:</code> to deliver a custom toolbar for my NavigationController, so I don't think I can use <code>initWithRootViewController</code>.</p>