Remove deprecated callback argument
Remove deprecated callback argument

Use loadCSS(...).onloadcssdefined( callback ) instead. or the onload extension. fixes #88
WeRockStar/loadCSS,geekz/loadCSS,eeebb/loadCSS,vovaane/loadCSS,vovaane/loadCSS,filamentgroup/loadCSS,filamentgroup/loadCSS,geekz/loadCSS,WeRockStar/loadCSS,eeebb/loadCSS