- Add scripts to be run inside a cibuildwheel docker image on both linux
   and macos which installs static versions of OpenBLAS (linux only), fftw,
   and suitesparse.  Link our internal _libtoast extension to these static
   packages, which ensures consistency regardless of other shared libraries
   loaded by other packages.

 - Add a github workflow which tests pip wheel building daily, and preserves
   the wheels as artifacts which can be downloaded and tested as needed.
   This also runs the unit tests on the installed wheel packages (linux and
   macos, python 3.6-3.8).

 - Add a deployment workflow executed on git tags which uploads to pypi.
   this will likely need some testing during 2.3.7 tag preparation.

 - Cleanup package definitions in setup.py, version generation, and add a
   MANIFEST.in file to ensure that extra package files are bundled.

…ess.