Info panel styling for MP pages

This branch adds a new, subdued panel style to the MP page, along with some cleverness for making sure two such panels, when placed side by side, are always given equal heights.

![screen shot 2014-06-26 at 15 21 11](https://cloud.githubusercontent.com/assets/739624/3399568/2d5b88ce-fd3d-11e3-8bfa-69194eeef7cf.png)

It covers three related issues:

* #496 – informational panels on MP page
* #504 – signposting the age and source of data
* #447 – mini survey on MP page

It also changes the way we install Foundation (to use a submodule, rather than relying on a global gem).

What this branch *doesn't* include is any actual information for the info panels, or any actual working mini-survey form elements. I'm guessing @jacksonj04 @mhl and @struan are best placed to sort those out.