Fix LessonBundle's create_from_course_bundle-method

See merge request !77

Do release 0.1.0.dev6

See merge request !76

Resolve "Implement bundled courses/lessons"

Closes #25

See merge request !50

Update pyproject.toml

See merge request !69

Update copyright and meta files

See merge request !67

Update .dev-js/package.json

See merge request !70

Update tox.ini

See merge request !68