Finalize v0.2.1

[kandersolar]

• [ ] Closes #xxx
• [ ] Added tests to cover all new or modified code.
• [ ] Clearly documented all new API functions with PEP257 and numpydoc compliant docstrings.
• [ ] Added new API functions to docs/api.rst.
• [ ] Non-API functions clearly documented with docstrings or comments as necessary.
• Adds description and name entries in the appropriate "what's new" file
  in docs/whatsnew
  for all changes. Includes link to the GitHub Issue with :issue:`num`
  or this Pull Request with :pull:`num`. Includes contributor name
  and/or GitHub username (link with :ghuser:`user`).
• Pull request is nearly complete and ready for detailed review.
• Maintainer: Appropriate GitHub Labels and Milestone are assigned to the Pull Request and linked Issue.