Changes betting increment

Rather than betting $1 at a time, BET + will now increase your bet in different increments depending on the size of your current bet. BET - will undo your last BET +. It's a lot easier to see when you play than me trying to explain it.

 **Current Bet** |  **Increase** 
--- | ---
< $15 | $1
< $50 | $5
< $100 |  $10
< $250 | $25
>= $250 | $100

If the increment is bigger than the money you've got left, it'll bet all your money instead.

I've done this for the poker game only. I can easily add this to blackjack as well if people like it.