Refactoring of playState to skinny coffee machine.

Getting no real advantage from the state machine yet, but tests are
passing. Time to see if I can get some improvements, then move on to
adding a third state to finalize betting.
Remove SkinnyCoffeeMachine for my own classes.

The difficulty here is not really in managing complicated state
dependencies and events, but in consolidating some logic into the states
themselves to remove conditional checks in a few different places.
More play state refactoring.

remainingMinutes, nextStateLabel, boardInstructions all retrieved from
state instance.
Bet round split into bet and settle.

During betting, bet and fold commands are allowed. During settle, only
call and fold commands are allowed. 'call' makes no sense while players
could still introduce a new, higher bet, and vice-versa.
Ensure folded players removed from game.

Fold would remove the player from the _pot_ - but wasn't removing them
from the game.