title: Get notified when something is added to NSPasteboard
body: <p>In my application I want to get notified if something is added into the NSPasteboard. If I copy an text from any other program  I want my application to know about it.</p>
  
  <p>Somewhere I read it can't be done that way. I should create a timer and check the content of the NSPasteboard myself.</p>
  
  <p>Is this the way to do? Or are there any kind of notifications?</p>