Fix flow

The markup is in totally the wrong order semantically, and on small devices (single column layout), the wrong content is at the top, sponsors and reviews is above events.

Should go

- Header
- Upcoming events
- Past events
- Twitter
- Posts
- The rest

Re-ordering it is simple enough but then the floating is all whack, "The rest", which is floated left, ends up in line with "Posts".

Suggestions? Masonry (bleugh)? CSS3 flow-whatever-it's-called? Something else?