title: Using SpriteKit in IOS, how do I implement 'snap' behaviour?
body: <p>I'm using SpriteKit to handle a bunch of smallish sprites on screen.  I'd like to tell one of the sprites to 'snap' to a specific location with the same kind of feel as that given by a 'UISnapBehavior' when used on a UIView.  I can apply a 'SKAction moveTo:' but I don't get the 'boing' at the end, which would feel nice.  I feel I'm missing something here as it is surely a common requirement.</p>
  
  <p>Thanks for any help - just a pointer will probably do...!</p>