Poetry environment

[openroadie]

I find poetry to be a nice tool to manage virtual environments (and it is extremely simple to use).

pyproject.toml: Top level dependencies poetry.lock: detailed dependencies (this only needs to be created once).

Also added a few lines in README.md on how to use poetry.

[openroadie]

Maybe these files should be moved to a subdirectory but I did not want to add one to this very clean repository.