make it look okay on mobile

This is a fix for https://github.com/npm/docs.npmjs.com/issues/14

It's a start:

![screen shot 2014-10-06 at 2 11 35 pm](https://cloud.githubusercontent.com/assets/2289/4533627/cbb81608-4d9d-11e4-879f-ed2857aa7337.png)

@isaacs this heading reminds me of Joe Pesci asking "How am I funny?" in that one gangster movie.

![screen shot 2014-10-06 at 2 11 26 pm](https://cloud.githubusercontent.com/assets/2289/4533622/c906df5c-4d9d-11e4-9fbc-ff973ea6990d.png)