Add more repo metadata.

[Poikilos]

• Add pyproject.toml (can be used instead of setup.py for most python versions)
• Add a separate _version.py for more cleanly importing it during install (without dependencies)
  • Use the standard __version__ variable, and import it from _version.py into __init__.py
  • Also, if you later add git tags to this repository then you can un-comment write-to in pyproject.toml to overwrite _version.py automatically
• Fix Classifiers are recommended by setuptools documentation rather than license="MIT". #37
• Fix Forward compatibility issue building PyAudio (installing old portaudio19-dev removes jackd2) #36

[anrayliu]

I'll definitely check this out within the next few days. I'm currently working on something big: removing cv2 as a dependency.

[anrayliu]

Merged, thanks a lot for your work buddy!