Some changes

Hi there, I know I'm a little late on this since 2.0 it's been worked, anyhow, here are my changes to 1.9. Hope are good  enough. (I'm really new to git ,so I'm a little confused right now about how this works):

FlxBitmapFont - Allows negative spacing while pixels do not overwrite.
FlxButtonPlus - Uses frame instead whole FlxSprite