Added value property to Card constructor.

Added a value property to the Card constructor that maps back to a values
object literal.
Added playCard and playRound.

Under the WarHand constructor, added a name value, as well as a function
called playCard that returns the first card in the hand's cards array, and
runs the .show() function on it.  Then added a playRound function that plays
a card from each player's hand, compares them, and adds them to the winner's
hand.