Updated SelectBoxIt v3.0.0 CSS file

Hey guys,

I had to make a quick adjustment/hot-fix to the SelectBoxIt v3.0.0 CSS file.  I updated the v3.0.0 tag in my repo to include the CSS update (https://github.com/gfranko/jquery.selectBoxIt.js/tree/v3.0.0/src/stylesheets).  Thanks again!

Greg