Update CSS to be based on 3.2 fixes

https://github.com/gilbitron/Nivo-Slider/commit/9a96048426847dbc0ea0236cd7d2cf8ae897489d#nivo-slider.css
Merge branch 'refs/heads/sandvox' into sandvox-regular
Merge branch 'refs/heads/sandvox-regular' into sandvox-retina