Component spacing

Added some margin to all components so the spacing is more consistent when placed next to each other. See demo at `/demo/spacing/`.
![screen shot 2014-06-12 at 4 17 00 pm](https://cloud.githubusercontent.com/assets/378023/3254910/2ad3c652-f202-11e3-9bee-985a7e7e2d5f.png)

Fixes #35, where the invisible pseudo elements were covering other components.
![pseudo](https://cloud.githubusercontent.com/assets/378023/3254925/987ea71c-f202-11e3-870e-4c1d3cdc16ad.png)