Drops the 'must-revalidate' bit, which prevents serving stale pages,
and sets a longer max-age to match the edge NGINX caching ttl.

Attempts to fix issue #114.

Avoids an extra SQL lookup on every request (a drop in the
ocean, but still).

It shouldn't be necessary in our setup, and it just makes keys
needlessly longer.

Merges the contents of ai3/docker/noblogs (composer branch).