Adding new closed data section
New Reqs added, closed section moved to challenges
Added links from UCs to new reqs, updated challenges table
HTML validation fixes
Fixing final validation error - I hope
Adding link from section 3.1 to reqs, making table of reqs section 3.2
Merge pull request #18 from philarcher1/gh-pages

Additions around closed data following 3 Oct WG call