Added a Changelog page

Which fetches data from the NEWS file in Picard's repo and builds an html version of it.

Live at: http://musicbrainz.github.io/picard-website/changelog.html
Apparently, cache: true is the default ajax() setting. I've tried all sorts of hacks (by setting cache-control headers and such) but just can't get this to work.

I'm now guessing that this might have something to do with rawgit's servers. The kind of response headers they send might be preventing the caching. This is just a thought though.