Move render info blurb out of redditfooter to avoid caches.

RedditFooter is a CachedTemplate and so the blurb which is supposed to
be unique to each request is being rendercached.
traffic: Generalize max-row highlighter and use on all columns.
traffic: Add explanation of which timezone the data is in.
traffic: Separate apart weeks in day-interval tables.

This should help to make week-by-week trends a little clearer and also
make it easier to see what day of the week a day was.
Indicate failure when no moderator invite is found.