Revert "add tile sets"

This reverts commit 449012a1f30fe040e426af18acab1a4d93267431.
changes

test background colors
tile

new tile set
Merge remote-tracking branch 'origin/master' into gh-pages

Conflicts:
	tile-sets/udacity/128.png
	tile-sets/udacity/16.png
	tile-sets/udacity/2.png
	tile-sets/udacity/256.png
	tile-sets/udacity/32.png
	tile-sets/udacity/4.png
	tile-sets/udacity/64.png
	tile-sets/udacity/8.png