Facet revamp

Revamp for module finder page sidebar:
- Able to reveal/collapse facets
- Persist the revealed/collapsed state of the facets
- Persist the checked/unchecked state of the filters

Fixes #109 and #46.

![screen shot 2014-08-02 at 3 15 02 pm](https://cloud.githubusercontent.com/assets/1315101/3787392/cee5f212-1a14-11e4-9839-967d65077a45.png)