Getting started instructions, proposal for Black formatting

[spra85]

Some of these proposals may be unwelcome, but thought I'd propose the introduction of the popular black Python formatter in addition to flake8 for consistent formatting.

Went down this path largely to initially make an update to the README for instructions on getting started, which wasn't immediately clear.

Assuming it isn't user error on my side, would be happy to address these failures in the local flake8 command within this PR:

py38: commands[2]> flake8 scourgify
scourgify/cleaning.py:14:1: F401 'typing.Any' imported but unused
scourgify/cleaning.py:14:1: F401 'typing.Optional' imported but unused
scourgify/cleaning.py:14:1: F401 'typing.Sequence' imported but unused
scourgify/cleaning.py:14:1: F401 'typing.Union' imported but unused
scourgify/validations.py:12:1: F401 'typing.Mapping' imported but unused
scourgify/validations.py:12:1: F401 'typing.Union' imported but unused

Hoping to learn more about these since it seems like omitting the typing may have been intentional with lines like this?

# type: (Union[str, None], Optional[bool]) -> str

However, there's mypy typing in most places within normalize.py. Let me know if I can help finish the typing push in the other modules.

Pending feedback on this PR, have another issue and PR related to address normalization I plan to submit for feedback.