Fixed the following bugs with Player:

1) Player no longer randomly changes direction (apparently 16*4+1 != 49)
2) Tapping the same movement button repeatedly now moves the charactes
3) Characters are now appropriately sized for the map (TODO: get the
size value dyanmically. It is currently hardcoded)

Fixes #54
Merge pull request #57 from nhandler/player_bugfixes

looks good