Extensive map changes

Involved a rewrite of most of the classes. Also working the ladder. How
do ladders work?! They stop physics but you initiate with the jump!?
Merge pull request #32 from rpwagner/master

Tile indexes being set to floats in Python 3
Merge branch 'master' of github.com:etinlb/TiledPlatformer
Merge pull request #33 from rpwagner/master

Added color backgrounds, removed executable bit from images