tests: add doctest to `events.bind` function.
tests: add doctest to handle functions.
handle: fix bug joining sets in handle_commit.
handle: refactor invalidate to avoid using transaction.
client: document and jig the config parsing logic.
client: add a provide-your-own IRedisClientFactory hook.
docs: update the readme.
tests: mark imports as pragma: no cover.
docs: tweak README again, adding tests section.