Merge pull request #30 from kalgynirae/grid-improvements

Add center, top_right, etc. properties to Grid
Remove the pusher before DeathErroring
Merge branch 'think-green-tweaks-2'
Add new high-rez super-HD graphics for floorpaint
added generate level to fllorpaint with player
added tiles, can't move through them yet
Clean up import statements
Add world.swap() to swap locations of two entities
[floorpaint] Get basic gameplay working
[floorpaint] Fix formatting in level generation
Merge branch 'floorpaint-generate-level-cleanup'

Closes #32