Move toCSV functions of FlxTilemap to FlxStringUtil
Merge branch 'dev' of https://github.com/HaxeFlixel/flixel into toCSV

Conflicts:
	flixel/tile/FlxTilemap.hx
Merge pull request #878 from Gama11/toCSV

Move toCSV functions of FlxTilemap to FlxStringUtil