Requested changes for M week

Adds changes requested ahead of the upcoming M-week.

Includes:

• Ensuring full compatibility with Python3 (pending an update to the hashing code)
• Updating build instructions to produce a setup file compatible with zsh as well as bash
• Addition of a command-line print out of a 'Jira/twiki style' table with a summary of the keys uploaded
• Comprehensive documentation (docstrings and comments throughout)
• Consistency & formatting changes (linted with Black, and changed to comply with flake8 standards)

Note: Going forward, new hashes generated will not be the same as existing hashes. See below for comment with details.

cc @jpanduro @mark @stelzer