use lumberjack for log rolling

This is very similar to the last PR, except I didn't change out the upstart config stuff... since the output redirect doesn't hurt anything, and we need the rest of the code to properly set permissions and owner on the logfile.
Are you sure this is enough? In environments experiencing a problem, I've seen the logs grow pretty rapidly. We don't want to throw away useful debugging information too easily, especially given that the really useful clues are often near the beginning.