Plans Comparison Page

## To merge before Sloth Launch :monkey_face: ##

This PR creates the Plans Comparison page, where customers can compare the features offered on each plan.

![screenshot 2014-07-24 23 31 05](https://cloud.githubusercontent.com/assets/651753/3697647/f7144946-13ac-11e4-9b73-f12106334278.png)

There are also some updates to be made, to facilitate clearer links between this page and the relevant documentation. If you come across something that could be improved in the links, drop a comment here!