feat(categories): show top level of categories.

#134
yes, the image build ok.

And the space is css (emulating the space in the design.) 

![screen shot 2014-12-15 at 12 01 08 pm](https://cloud.githubusercontent.com/assets/2622152/5433626/1df85d48-8452-11e4-870e-c827d1da81bb.png)
![screen shot 2014-12-15 at 12 00 55 pm](https://cloud.githubusercontent.com/assets/2622152/5433627/1dff056c-8452-11e4-9776-c6d78279edfa.png)