New nav design: swipable horizontally

![nav-swipe](https://cloud.githubusercontent.com/assets/85783/3326742/05f1e33c-f7a2-11e3-9289-bf939d549f80.gif)

Prototype: http://kaelig.github.io/guardian-navigation-prototype/

Not fully sure why I had to commit some dotfiles again.

![ ](http://media.giphy.com/media/NnKeUEK4D4Jck/giphy.gif)
The `breadcrumb` schema markup should go on the tiny little crumbtrail currently at the bottom of the page, not these