Fix toKeyString to not mutate state.
Merge pull request #2 from abliss/master

Adds a shortcut for generateHands in the common last-street case.
Fix fromKeyString for fouled hands.  This all seems very dicey.
Adds a shortcut for generateHands in the common last-street case.

On my system, provides a 43% speedup for the calculation of 12th street.
Cache the 52 possible results of createCardMask.

21% speedup on my machine.
Merge branch 'master' of https://github.com/ejwu/ofc