v4.0.0

This release cleans up the API and makes a lot of breaking changes. Especially so because it was renamed from PyPython to PySi.

What's Changed

• Bump protobuf from 3.17.3 to 3.18.3 by @dependabot in #2
• Large refactor/restructure of classes and module layout by @saultyevil in #11
• Bump astropy from 5.2.2 to 5.3.3 by @dependabot in #12
• Bump tqdm from 4.64.1 to 4.66.3 by @dependabot in #13

Full Changelog: 3.2...v4.0.0