Release v5.1.0

fix: typo in `CONTRIBUTING.md`

Merge pull request #767 from EducationalTestingService/release/5.0.0

Release v5.0.0

Merge pull request #756 from EducationalTestingService/release/4.0.1

Release v4.0.1

fix: unnecesary str -> Path conversion in tests

Add runtime.txt to override python 3.7 in binder.

Update version number and copyright years.

SKLL Release v3.0.0

SKLL v2.5 Release

SKLL Release 2.1