Minor changes

* move the artist page out into it's own module
* add average artist ratings to explore page
* add a slight shadow and spacing to album list (helps with white album covers) and fix album cover width.

![screen shot 2013-08-19 at 12 55 00 pm](https://f.cloud.github.com/assets/805358/987587/25f2d462-08f0-11e3-8d48-a4a70c494514.png)

![screen shot 2013-08-19 at 12 55 18 pm](https://f.cloud.github.com/assets/805358/987588/27a97d6a-08f0-11e3-9ccb-5c2048d90230.png)