Contribution getting started

Contributions are highly welcomed and appreciated. Every little bit of help counts, so do not hesitate!

Contents

Preparing Pull Requests

Fork the repository.
Enable and install pre-commit to ensure style-guides and code checks are followed:
```
$ pip install --user pre-commit
$ pre-commit install
```
Afterwards pre-commit will run whenever you commit.

Note that this is automatically done when running tox -e linting.

https://pre-commit.com/ is a framework for managing and maintaining multi-language pre-commit hooks to ensure code-style and code formatting is consistent.
Install tox:

Tox is used to run all the tests and will automatically setup virtualenvs to run the tests in. Implicitly https://virtualenv.pypa.io/ is used:
```
$ pip install tox
$ tox -e linting,py37
```
Follow PEP-8 for naming and black for formatting.
Add a line item to the current unreleased version in CHANGES.rst, unless the change is trivial.