bug 1004756 - home page promo for World Cup 2014

*DO NOT MERGE* 

This promo isn't scheduled to go live until June 12. I'm filing this PR now to get the ball rolling on code review and l10n.

@flodolo: you can add these new strings to home.lang at your earliest convenience. The promo is viewable at https://www-demo4.allizom.org