Add package docstrings for spreads and spreadsplug
Fix typo in spreadsplug docstring
Add docstrings for spreads.main
Refactor argument generation
docs: Add sphinx autohttp and aafig extensions
Docstrings and more comments for spreads.cli
Fix tuple literals in spreads.main
Refactor colored printing on CLI
JSON-serialize a Path to its absolute value

... if it is not part of a BagIt-compliant directory
More docstrings for spreads.util
Docs: Fix typo in CLI section of README
Docs: first attempt at describing a developer environment
Added a couple more prerequisites for the dev env