Columnar Footer Nav

Implementation of https://github.com/npm/newww/issues/254

I will now pass this potato request to @seldo, who is going to write docs for:

- [ ] private npm
- [ ] security
- [ ] about npm Inc

Looks like this on a laptop:

![screen shot 2014-11-13 at 4 41 29 pm](https://cloud.githubusercontent.com/assets/2289/5039526/2dc7a196-6b54-11e4-8915-831a3aa5f3e8.png)

And like this on a laptop pretending to be a mobile device:

![screen shot 2014-11-13 at 4 41 42 pm](https://cloud.githubusercontent.com/assets/2289/5039529/30d471f2-6b54-11e4-99b3-6381b1acf460.png)