Prep for new release

[jhtu]

Need to check code before new release.

[jhtu]

Task list:

• Update ERA tests
• Move transfer function code into a branch
• Run all the tests
• Update release notes
• Update the version number
• Tag the commit
• Consider new webhosting service for docs
• Consider setting up conda package
• Clean up branches on github
• Upload to PyPI

[jhtu]

@belson17 I think we are close to ready for the release of v2.1.0. I pushed the releaseprep branch up to github so you can see it.