CardMatchingGame removes cards from play once they are matched.
CardMatchingGame now sends notifications when cards are added and removed and the Controller updates the UI appropriately.
Introduced a "Cards" property separate from the "InternalCards" for the Controller to know what cards are in play and not rely on the cardAtIndex method.
Method drawAdditionalCards added to allow user to draw additional cards.

CardGameViewController - Refactored and tweaked some of the animation code in the controller.

CardView.m - BugFix: Was setting negative line width.