Coding standards and linting code

[stevavoliajvar]

For everyone to be on the same page it's best to use some coding standards, like PEP-8 for example. We can also add a linter like black, flake8. They can also reformat the code so people can just focus on writing it and the tools will do proper formatting. Pre-commit can work well with that, so it does formatting just before commit and that way ensures code quality to some degree.

We should add .pre-commit-confg.yml to this, and instructions for using it into README.md.