Rc 0.2.0

[austinorr]

This PR is intended to prep the package for a public release.

Goals are:

• installable with minimal requirements (pytest is not/should not be required). test that package works with minimal pip install during CI
• declare requirements and dev-requirements in setup.cfg
• update setup.py to track versions correctly in preparation for pypi release.
• drop unmaintained and unneeded developer & CI tools (generate_vtasks.py, check_cloudside.py, travis)
• consolidate CI actions that have the same triggers
• improve flake8 style and black format conformance
• update Readme (and code where needed) to include a working example.

closes #55
closes #54
closes #53
closes #52
closes #46

[austinorr]

@phobson I think this PR is now ready for final review. Please take a look at my alterations to the validate.axes_object function. Hopefully this is a good enough solution that avoids importing pyplot and still delivers a plot back to the user if ax=None

[phobson]

Looks good. Do you want the honors of merging?

[austinorr]

closes #55
closes #54
closes #53
closes #52
closes #46