Stop relying on self.task_id
Streamlined update_state usage

Switched from kwarg usage to arg
Some minor clean to improve memory usage
Added George Marshall to AUTHORS. Thanks George!
Refs #17 Pyflake fixes. Hooray flake8
Refs #17. Added a test using the PROGRESS status.

This test fails against master, illustrating the bug.
Refs #17. Added a changelog entry.
Merge pull request #17 from PolicyStat/issue_17

Closed #17. Don't rely on self.task_id