title: UITextField -- observe changes to selectedTextRange?
body: <p>Is there any way to observe changes to the selectedTextRange of a UITextField?</p>
  
  <p>I tried observing all UIControlEvents.  But changing the selectedTextRange does not trigger a UIControlEvent.</p>
  
  <p>Another dead end -- UIKit classes are not KVO compliant.</p>
  
  <p>Then there is the UITextFieldTextDidChangeNotification.  But that's for changes to the text.</p>
  
  <p>Any ideas?</p>