Use declarative setuptools configuration setup.cfg

[mwtoews]

Use a declarative configuration setup.cfg described here to move most static metadata from setup.py, which is now only used to support versioneer. Other changes:

• This GitHub repo was not described in PyPI, now updated with url
• README.rst had syntax errors in markup and would not be rendered on PyPI, fixed using conventional RST markup for image
• Add pyproject.toml to describe build system requirements
• Modernize Makefile

[coveralls]

Coverage remained the same at 0.0% when pulling 3f80c1a on mwtoews:setup-cfg into 3209cd1 on csdms:master.

[mcflugen]

@mwtoews Amazing! Thank you! 🎉

This is something that's been on my to-do list for a while.