Hgicommon

Added
- Helper to get open port.
- Manager to control temp files.
- Code to help with creating unittests that run the same tests on multiple types.
- Function to help use tests that can either test all classes or just the "latest" one, depending on the setting of an
environment variable.
- Function to extract version numbers from strings.

Added
- Code to help with using Docker.
- Random string generator.

Added
- Counting lock.
- Exception suppression decorator.
- Support for hosting on PyPI.

Removed
- Unused JSON serialisation code and subsequent dependency on `hgijson`.

Changed
- Fixed thread-safety issue in `Metadata` ([8](https://github.com/wtsi-hgi/python-common/issues/8)).

Added
- First stable release.