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.
If I'm honest, I'm not fond of these vanity urls - especially if we start to have a large number of them but I know they're basically accepted. Is there any plan to move  this into the juju org?