title: UIActivityViewController on iOS 8 show "more" button with custom activities
body: <p>Now XCode 6 with iOS 8 SDK is out, we can talk about stuff.
  I tried to use custom activities with UIActivityViewController on iOS 7, everything worked fine.
  But on iOS 8, when custom activities are shown, there is "more" button sitting next to them and clicking on this button show exactly the same custom activities.
  Did anyone find a workaround to remove this button? I couldn't find any solution yet.</p>
  
  <p><img src="https://i.stack.imgur.com/4QKti.png" alt="Redundant More button"></p>