title: Detecting addon uninstall event on FF4
body: <p>How can I detect when user has uninstall my addon on FF4 (for cleanup process)?
  While it's working well on FF3, it does not work on FF4 beta...</p>
  
  <p>I've tried this code sample: <a href="https://developer.mozilla.org/en/Addons/Add-on_Manager/Code_Samples" rel="nofollow">https://developer.mozilla.org/en/Addons/Add-on_Manager/Code_Samples</a></p>
  
  <p>Does anyone know how to solve this?</p>
  
  <p>Do you know of addon that support FF4 and has this event listener?</p>
  
  <p>Thanks!</p>