Alfred-pyworkflow

Alfred 2 has been fixed.

Workaround for 80.

- Add prerelease option for updates 77
- Make writing of settings.json uninterruptible 79

Thanks to idpaterson for the above new features

- 74 fixes long-standing issue that POST requests weren't POST requests without any data.

The unit tests have been heavily overhauled to use py.test and run entirely offline. This
makes the tests run on Travis CI again.

- Fix broken handling of mutable values by Settings
- Ensure settings.json is only written when Settings has changed