Check that we don't serve stale data.
Check that we don't serve stale data.

In particular, if our data is more than 6 hours old, respond with 500
Internal Server Error to all requests, because someone should investigate
the problem.  That's much better than serving stale data and either nobody
noticing or relying on clients to check timestamps.

fmapfmapfmap/onionoo-dev,fmapfmapfmap/onionoo-dev,fmapfmapfmap/onionoo-dev