Consider compatibility with PEP-518

**Is your feature request related to a problem? Please describe.**

We should consider compatibility with PEP 518. Either using modern packaging tools like `poetry` or just using the plain `setuptools` but in a modern way.

**Describe the solution you'd like**
Add a `pyproject.toml` compatible with `setuptools`.

**Describe alternatives you've considered**
n/a

**Additional context**
https://www.python.org/dev/peps/pep-0518/