Fix Tilemap on game resize
Better doc for _helperBuffer
DRY
Minor optimizations
Minor fixes
Better doc for _helperBuffer
Merge pull request #978 from JoeCreates/dev

Renamed setOriginToCenter() to centerOrigin() in FlxSprite.
FlxSprite: move centerOrigin() next to centerOffsets()
Merge branch 'fix_tilemap_buffer_with_signal' of https://github.com/kevinresol/flixel into dev
Fix potential issue with group collisions (thanks @JoeCreates, 8a7d6cbc2863915fb2597c1000dfa3d95fb12f71)
Fix issue with #977 on state switches / properly clean up the signal listener