Potential bug fix for joining.

When 2 players simultaneously attempt to join a game with already 3
confirmed players in it, the confirmed players should reject at least
one of them. Therefore, they need to check whether the number of players
which may end up in the game (as opposed to just those that are
currently in the game) doesn't exceed the maximum number of players.
Added vote requester to facilitate implementing voting mechanisms.
Rewrote join requester as a vote requester.
Moved string constants to separate Constants.
Merge pull request #24 from tgoossens/vote

Added vote requester to facilitate implementing voting mechanisms.
Implemented maze tile sharing.
Added overload for sendTiles.
initial seesaw proposal
Merge pull request #20 from tgoossens/tile

Share maze with partner.
implemented seesaw locking model. Tested. Only flaw: simultaneous locking
removed sysouts
Publish the result of the lock request to the callback.
Code clean up.
Small fix in method signature of SpectatorClient.stop()
Unlock shouldn't need the seesaw barcode as argument.
Cannot request lock when already holding a lock on a different seesaw.
Fix error messages.
Separate player number and object number.
Player numbers range from 1 through 4, object numbers range from 0 through 3.
Pass object number to PlayerHandler.gameRolled()
Remove request before acquiring a seesaw lock.
Remove unused seesaw request constant.
Merge pull request #9 from tgoossens/wip

Communicate about locking and unlocking of seesaws.
Removed constants for unimplemented match and meet messages.
Share position with team partner. Fixes #25.