Maintain dependencies in setup.py

[wtgee]

Move dependency list to setup.py and use use the pip-compile tool introduced in #907 to generate requirements.txt.

Describe the solution you'd like
The definitive list of dependencies should be kept in setup.py to be compatible with setuptools but there should also exist a requirements.txt version for pip installing.

#907 introduced the use of pip-compile (from pip-tools) for auto-generating the requirements.txt file from a requirements.in file. We should instead keep the list of dependencies directly in setup.py and remove the requirements.in file completely.

Related Issues/PRs
#907

[capsulecorplab]

This is also achievable with the pip-tools toolchain; If the dependency list is specified in an install_requires in setup.py, then you can generate requirements.txt from setup.py, using pip-compile without any arguments, or pip-compile --output-file requirements.txt setup.py to update.
See requirements-from-setuppy

This also happens to be the recommended configuration by the PyPA User Guide 🙂
https://packaging.python.org/discussions/install-requires-vs-requirements/

[wtgee]

This is also achievable with the pip-tools toolchain; If the dependency list is specified in an install_requires in setup.py, then you can generate requirements.txt from setup.py, using pip-compile without any arguments, or pip-compile --output-file requirements.txt setup.py to update.
See requirements-from-setuppy

This also happens to be the recommended configuration by the PyPA User Guide
https://packaging.python.org/discussions/install-requires-vs-requirements/

Thanks @capsulecorplab, that's what I did for a different repo, I just need to clean this one up a bit before. Cheers!

[wtgee]

This was completed as part of #937