Website overhaul

Preview available at: http://geraintluff.github.com/json-schema/

The current site is hard to read, and not very engaging.  I tried to make something a bit bolder, as well as stream-lining the front page and giving it a summary of why our format is awesome.

All the information from the old site should be there - shout if you find something that's not, and I'll fix it.