0.6.0
-----
- Tolerate missing optional metadata (written as 'UNKNOWN')
- Support src_root for sources in ./src/ etc.

0.5.0
-----
- Update enscons.setup2toml
- Support --dist-dir as needed by tox (write sdist to given directory)
- Improve documentation

0.4.0
-----
- Introduce env.Whl() to gather wheel members and env.WhlFile() to
  finish the archive
- Add env.SDist(source=...) to automatically name source archives.

