World Cup 2014 wallchart

This PR introduces an early preview of the new wallchart. A new endpoint, /football/:comp/overview[/embed] exists and for the world cup will display the World Cup Wallchart!

/football/world-cup-2014/overview

It isn't quite finished (although it now displays just fine) but we need to release it so we can test it through R2 and mobile while we finish off the details. The paths have been added to the router but there are no links pointing at this page.

The overview page works generally for all competitions but in the case of the world cup a list of hard-coded match dates are provided to generate the correct ordering for the wallchart knockout stages visualisation.

The wallchart will be embedded in an article and thus made available on a content URL so that it can be pulled into mobile apps and R2. It's essentially an interactive.

Here are some screenshots of the feature:

Knockout stages for world cup:
![wallchart-pr](https://cloud.githubusercontent.com/assets/29761/2928800/a9c1529a-d781-11e3-9770-dbf8a4272666.png)

Excerpt of the group stages:
![wallchart-pr-groups](https://cloud.githubusercontent.com/assets/29761/2928804/acadfb0c-d781-11e3-89ce-1ca7dd9ae35d.png)