changed getSpriteSheetFrameKey(), getKeyForSpriteSheetFrames()
changed getSpriteSheetFrameKey(), getKeyForSpriteSheetFrames()

this fixes issue described at:
http://forum.haxeflixel.com/haxeflixel-development/pic-flxtilemap-grid-layout-issue-after-upgrading-from-20-to-30

HaxeFlixel/flixel