Document test dependencies

[sebastic]

The werkzeug dependency was not documented.

[lonvia]

The new dependency is 'pytest-httpserver', which pulls in werkzeug. This is mentioned in the README but I forgot to add it to the release notes. Sorry about that.

I spend some time yesterday researching what is the approved way to specify test dependencies. Seems there is none. So I left it with the comment in README. Would it help packaging to have the extra-requires instead?

[sebastic]

The new dependency is 'pytest-httpserver', which pulls in werkzeug.

test/test_replication.py imports werkzeug, hence the explicit dependency is required.

Would it help packaging to have the extra-requires instead?

Yes, it makes the test dependencies explicit just like a requirements-test.txt file would.