Prepare release 2.3.7

[mcmtroffaes]

@graingert Anything else needed that you can think of? Can you think of any good upstream projects or high profile users which need this package that might be interested to help testing this?

[mcmtroffaes]

Is this good to merge (conditional on #69 being merged)? I'm still waiting for a response on your py.typed related comment @graingert

[mcmtroffaes]

A heads up that I'll be merging this shortly (unless someone still wants to raise an issue).

[mcmtroffaes]

Will be tagging in a moment, we'll find out if the release script does it's job as intended... 🤞

[mcmtroffaes]

The release script failed:

https://github.com/jazzband/pathlib2/runs/5109176234

Not sure why. Anyway, I've done a quick manual release so it's on pypi.

[mcmtroffaes]

Just to note I've had to yank the release (and, the post release that tried to fix the problem), due to a dependency issue and python2's pip being too old to properly resolve dependencies (who knew...). I think for future pure python 3 releases we best bump the major version number for upstream projects still on python 2. I have some cleanup PR coming up which will take care of this.