Help videos A/B results - watched more videos?

Shows which style per-level yielded more additional videos watched.
redesigned the contribute page
Merge branch 'master' of https://github.com/codecombat/codecombat
Help videos A/B results - sub followed?

Shows which level/style combo was followed by a sub purchase.
Separating contact emails into premium subscriber support and basic general support.
Upgrading contact form context a bit.
Merge branch 'master' into production