Do not crash upon selecting a key on the command-line if there already is a
key stored in the configuration. (#5)
Create the configuration directory upon saving, if it does not yet exist.
(#6)
Isolate the tests properly and consistently from the user’s configuration, so
that user configuration problems do not cause unrelated test failures. (#8)
Add an alternate MkDocs configuration for building the documentation in
offline mode.
Fix typing issues according to mypy’s strict mode.
Include and exclude the correct files in the sdist and wheel
distributions. (Previously, sdist contained VCS artifacts, and wheel was
missing some paths.)