Add .pre-commit-config.yaml for local setup

[lebrice]

Devs can optionally turn on pre-commit locally using:

$ pip install pre-commit
$ pre-commit install

Then, the following actions are performed on the diff before it is committed locally:

• black: Reformat the code using black
• codespell: Check for spelling mistakes
• flake8: check for various code quality issues
• isort: sort imports
• pyupgrade: Remove outdated python syntax stuff from the code (e.g. super(thing, self), etc)
• autoflake: Remove unused imports

If any of the above hooks fail, the commit is interrupted, the differences get added as modifications, and the user can add them before the commit goes through.

It's really simple and convenient.

The only thing that I'm not 100% sure about is codespell, which I think might generate a bunch of false positives. Even then, it's always possible to just add words to the ignored words list, as needed.

[lebrice]

Fixes #892

[bouthilx]

It would be great to reuse this for the tests instead of duplicating them. It would help avoid mismatches when we update black version or some configuration in tox. May be worth creating an issue.