add choice of the type of virtual environment for pip, pipenv or poetry.

[haricot]

This Pull Request propose to have the choice of the type of virtual environment for pip, pipenv or poetry.

[jrief]

I agree that this is a good solution. However, I would rename the Cookiecutter variable into something more descriptive, maybe pip_dependency_manager or similar. I'm open to any other proposals. Reason is that for instance Poetry introduces itself as

Poetry is a tool for dependency management and packaging in Python.

whereas pipenv says:

Pipenv is a tool that aims to bring the best of all packaging worlds

and piptools

A set of command line tools to help you keep your pip-based packages fresh

Speaking of pip-tools, wouldn't that be another candidate?

[haricot]

Totally agree, I will change it for pip_dependency_manager Piptools looks really nice, I didn't know about this approach which corresponds a little in the end to the pipenv.lock ot poetry.lock but a little more manual which has these advantages. For the pyproject.toml format, there is a specification https://www.python.org/dev/peps/pep-0518/#id25

[jrief]

Thanks