first draft of blackjack as sent to insight fellows program.
contains:
- multiplayer play
- multideck shoes
- splitting (one split max per player)
- insurance
- doubling down
- blackjack pays 2:1 (generous, *integer* payouts)

also has minor fixes which include keeping dealer card face down
after checking for blackjack, and 21 tiebreaking in favor of player
blackjack.