Write main application loop to build a hand of cards

Add main method to Hand.
Repeatedly ask user to "hit" or "pass".
If the user hits, another card must be added to their hand. The new hand is displayed.
If the hand goes bust after hitting, a message is displayed to the user and the application terminates.
If the user passes, the application terminates.

Depends on #21

CoderanchCorral / Blackjack