Popular audio 

Adds 'Popular audio' to RHC on Audio pages

Also tidied up class names and css

![screen shot 2014-07-29 at 16 52 22](https://cloud.githubusercontent.com/assets/74132/3737598/7f6dbd8e-1738-11e4-85e0-1a5aff371894.png)
 
can you update the func name?