Only run football snap JS on footaball snaps

Running the football JS on non-football snaps will cause trouble.
In fact it has already with the fronts team.

[This was the original commit](https://github.com/guardian/frontend/pull/5443).

__//cc__ @sammorrisdesign @tudorraul 

![Snap](http://stream1.gifsoup.com/view6/3968873/zoidberg-z-snap-o.gif)