CSS suggestion

Changed background and border color in odsaAV.css and show/hide button css in odsaMOD.css and odsaMOD.js

AV CSS:
- The AV background is now a bit grayer
- The AV border is now dark (gray) green instead of black
- The instructions also have the same darker green color for the border

Show/Hide Buttons:
- The buttons now look a bit more like [Twitter's Bootstrap](http://getbootstrap.com/)
- White text color
- Rounded edges
- Dark hover effect
- The yellow color has been replaced with (a yellowish) orange