/latest/: use an absolute redirect, update tests

[abrasive]

This avoids an issue where the redirect is interpreted as a relative
URL.
This is caused by an update in one of the dependencies.
Resolves #28.

While I'm at it, updated one of the tests, because recent versions of
Werkzeug return a 308 for a permanent redirect. This is like a 301, but
preserves the request, including if it is a POST.

This fixes the tests on CI where it doesn't use the Pipenv.lock.

[abrasive]

I took the liberty of giving Python2 the flick from tox.ini - while it's admirable that you have supported it so far, judging by the CI logs, some of the dependencies have moved on! My apologies if that was presumptious of me.

[rgalanakis]

This is great! One ask- since this is a big backwards-compat change, can you add a CHANGELOG.md file and note that version 2.0 is Python 3.3+? I'll cut a version 1.0 before releasing this version.

Since this is not a library, and not so actively developed, and 2.x is near EOL, I'm okay finally removing it. I wanted to hold on because this tool is mostly for enterprises and they move slow :)

[abrasive]

I certainly can, do you want to start the CHANGELOG at 1.0 and I'll rebase on top of that?

[rgalanakis]

Thanks for this! Happy that CI is passing again 🍾