Add mobile detection and serve a mobile-specific site.

Tested on Firefox Mobile (on Galaxy S3 mini):
- On group page, tap on team to highlight its matches
- On Finals Board, tap on "Round of 16" to display a tooltip with the groups they come from
- On Finals Board, tap on Quarter or Semi finals to highlight where they come from
- Fixed width, centered, on landscape orientation
- You can force the mobile site on desktop by adding ?mobile in the url (before the hash of course)

Comments welcome.
Release version v0.7.0