Fixed the ribbons style

The ribbons style was applied to the image box, It doesn't work well especially for the twitter bootstrap navbar-fixed. Also it was missing the z-index to be on front.

How it was before:
![screen shot 2013-10-23 at 04 45 35](https://f.cloud.github.com/assets/108663/1387422/a5acb8d0-3b95-11e3-956b-d1135b87ac68.png)

How it is now:
![screen shot 2013-10-23 at 04 47 19](https://f.cloud.github.com/assets/108663/1387432/efd07cf8-3b95-11e3-8d67-1afd89f34dd5.png)