updated playingCards to remove themselves after matching
finished 4.4 - added ability to add 3 cards to Set game and update UI
4.5 - added transitionWithView animation for card touches at superclass level
4.6 - new cards animate from bottom-right in
4.7 - when redealing, send cards from lower left
4.8 - updated for auto layout issues
4.10 - adding pinch and pan behaviors to game card views