Update documentation and release 3.0.1

Changes that need to be documented:

[ ] Note: now requires Python 3.6+
[ ] New non-string path DBF access: filedata + memofile/ignore missing memo args and ignored path arg.
[ ] Check / update check README.rst & changes.rst
[ ] Create examples of access without string path, including access within a zip archive
[ ] Get docs building at https://catalystcoop-dbfread.readthedocs.io
[ ] tag and release v3.0.1

catalyst-cooperative / dbfread