Migrate to organization

[bmcfee]

This was discussed in #370, but we agreed to migrate this repo to a dedicated organization. (mir_eval?)

There are a couple of other things that will need to be squared away when we do this:

• update author in README and setup.cfg
• update copyright in sphinx docs
• update all URLs to point to the new home. (GitHub will redirect this automatically, and we can use sphinx linkcheck to identify this automatically in a CI action.)
• update badges in README
• manage permissions for integrated services, codecov, pypa, zenodo, readthedocs, etc

Feel free to add to this list as needed.