Prepare release v0.3.1

Merge #33

33: Prepare for release 0.3.0 r=bertptrs a=bertptrs

Double check

- [x] documentation
- [x] changelog
- [x] tests


Co-authored-by: Bert Peters <bert@bertptrs.nl>

Bump version

Merge pull request #15 from bertptrs/pre-release-cleanup

Prepare for relesae

Prepare for release

Prepare for release