New-style debate page

The first instalment of #555. A new design for the debate page.

![screen shot 2014-07-18 at 14 51 17](https://cloud.githubusercontent.com/assets/739624/3626852/a369610c-0e82-11e4-993b-19f0455cae21.png)

Currently only debates or speeches accessed via their ID (eg: /debates/?id=2009-10-29a.479.0) will get the new design. Everything else gets the old design.

And the new design doesn't show user-submitted annotations, or videos, yet.

The integration tests assume you have a database set up with debates from the last week of October 2009 (the only data I had to hand, in the absence of a fixture database). If you run the tests you'll see 4 failures, which correspond directly to the 3 technical blockers stopping this from being deployed:

- [ ] I can't work out how to set the `<title>` of a page via the new `Renderer` class.
- [ ] I can't get `$GLOSSARY->glossarise()` to work.
- [ ] I can't verify `$SEARCHENGINE->highlight()` works because I can't get Xapian running (see #586).

Design-wise, I think this is good enough to get out there, and iterate later – there are still rough edges, but, once some developer time is put into fixing the three issues above, I think we should deploy asap.
That's correct. We could add the section heading back in, but at the expense of cluttering the page up again. If we were to do it, I'd like to see examples of popular pages where the subsection alone makes no sense.