Refactor #4856: Refactor CCTMXLayer's API with pos parameter to support both pos and x, y parameters
fix bug
refactor getTileGIDAt,setTileGID,removeTileAt,getPositonAt in TMXLayer
Merge pull request #323 from joshuastray/master

Refactor #4856: Refactor CCTMXLayer's API with pos parameter to support both pos and x, y parameters