Remove h2 from footer

Having a h2 in the footer can be confusing as it demands more importance
than content in the page. Replace the h2 with a paragraph, this means
that the content can still be found and read by someone looking for the
licence information.
Add rel=licence

As suggested by Brad Wright, add the appropriate relationship.

[1]: http://www.w3.org/TR/html5/links.html#link-type-license
Merge pull request #99 from alphagov/remove-footer-heading

Remove h2 from footer