#17 Advanced Features - Double Down

[Jia Lu]

As a: Player
I want to: be able to double down my bet, at 100%.
So that I can: utilize my chips with strategy.

AC 1: Double down is available when a player has two cards at hand.
AC 2: When a player choose double down, a player commits to an extra 100% of original bet.
AC 3: When a player choose double down, a player commits to stand after the next card.

[Kuo Wu]

This will have to be another button, which checks on player's available currency, and disabled after 3 cards has been dealt.