title: SceneKit collision didbegincontact change with Xcode 7
body: <p>I have a SceneKit game that the character is set to collide and collect collectables within the game. This is done using the standard collision masks and was working perfectly until I updated to Xcode 7.</p>
  
  <p>Now although the collision is happening the didbegincontact method is not being called.</p>
  
  <p>Is there a change I missed to cause this? I have check the delegate declaration and reviewed changes made line by line.</p>