ALL: Improvements across the board

 - Main program significantly cleaner, event-driven
 - Played around with sprite animation. Player now changes direction.
 - Played around with targetted motion. Dog now follows player, more or
   less
 - More documentation
 - Moved models.py --> players.py, cause that makes more sense
 - Added CREDITS to keep track of where external things are coming from
 - Researched a little into map-making, see README