Version 2.1.0: Use entry_points for plugins

Bug fixes:

• Fix job --pid under python3 to display output correctly (instead of byte-array
  repr string)
• Stop printing a backtrace when handling KeyboardInterrupt in job -w.

Changes:

• Use the entry point 'wwade.jobrunner' for plugin loading. Deprecate the
  'jobrunner.plugin' module, to be removed in 3.0.0.
• CI updates

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.

Version 1.0.6

• Improved performance by caching database cursors.
• Properly quote command strings in job info detailed view (job -s, job -l -v).
• CI improvements (add test output / report integration for Azure, improve integration test reliability).
• Improve job --interrupt use of sudo when killing jobs started with sudo.
• Skip reminders in normal job list (can be shown with job -ll).
• Only show summary of reminders in job watch (job -W).

Version 1.0.5

- Significant performance improvements in "query" commands (list, job info)
- Bug fixes.
- New `--monitor` option that uses `tail -f` immediately on the new job's
  log file.