Bug 1054437 get involved redesign

Probably needs a bit more polishing and tidying but it's complete enough to start code review.

Run <code>./manage.py cron update_reps_ical</code> to fetch events if you don't already have them.
I don't think it's required, and when I try adding one it messes up the link and opens in both a new tab *and* the current tab. Unless I'm doing it wrong...