Make some pages responsive (global nav, docs layout)

* Fix browser width of landing intro section
* Optimize layout for docs in different media sizes
* Make responsive global nav

https://trello.com/c/yPplScUQ

![screenshot 2014-11-20 17 33 53](https://cloud.githubusercontent.com/assets/816402/5136357/7578a724-70db-11e4-8866-3ffa2ddb128d.png)
![screenshot 2014-11-20 17 33 59](https://cloud.githubusercontent.com/assets/816402/5136358/75867840-70db-11e4-9117-175aad9eaa09.png)