Introduce project guidelines: code style, docstring style, formatter, linter, etc.

[majabojarska]

As this little project is gaining traction, it would be good to introduce code guidelines. Specifically docstring style, formatting and linting tools. Everyone has some coding habits and prefers some tools over other. However, in a project it would be best to agree on some rules, just to keep the codebase clean and uniform.

This is obviously a topic for discussion. From my side, I'd like to propose the following:

• PEP8 code style, as it's the official Python style guide. To check for code style compliance, a linter should be used, such as Flake8 or Pylint. Both check the code against PEP8. Pylint is stricter, but also more elastic. Both Flake8 and Pylint can be tweaked if necessary. I would go with Pylint after all.
• Black formatter, as it is PEP8-compliant and has sensible defaults. It can be run also as a pre-commit Git hook to format the codebase on commit. Integrates well with various editors and IDEs.
• Numpy docstring style. It's pretty common and well supported. Can be paired with Darglint to lint docstrings.

The above guidelines can be later described via a CONTRIBUTING.md file together with the preferred contributing workflow.

[Prayag2]

OOOOHHHH this is awesome! I didn't know about any of these! The last one is really amazing! I never knew that I needed it so much! Thank you!! I learnt a lot from you!

[Prayag2]

Please have a look at #27

[majabojarska]

#27 Is already merged. I left some feedback over there.

[majabojarska]

Added Black and PyLint as dev requirements in #30.