Version 2.0.0: Major release with incompatible database change

When upgrading from 1.0.6 or earlier, your database will no longer be usable. The
best option is to back up the log directory, if needed.

This new version also adds support for python3 along with a number of smaller bug
fixes and improvements.

Added a 'chatmail' script that can be used with google hangouts chat for job
completion notifications (job -m). More info available in the README.