Renaming FlxString to FlxStringUtil.
Merge branch 'dev' of https://github.com/HaxeFlixel/engine into dev

Conflicts:
	flixel/util/FlxStringUtil.hx
	src/flixel/util/FlxString.hx
	src/flixel/util/FlxStringUtil.hx
Merge remote-tracking branch 'origin/dev' into dev
Merge branch 'dev' of https://github.com/HaxeFlixel/engine into dev
Removing file that I put in wrong location... oops.