Switch to Python >= 3.5 and fix latest aiohttp compatability

[sarayourfriend]

Fixes #82. In doing so it was necessary to fix everything that used Python 2 and anything older than 3.5 (in order to use async def). This required updating some dependencies.

This appears to work, however I'm not able to run the full test suite as the Nose library, used to run the nose_suite tests, is not compatible with the latest Python versions: nose-devs/nose#1118

Potential solutions are: only actually run the nose tests in Python versions up to the latest version supported by Nose (which has been unmaintained for 6 years). I believe this is Python 3.8 or 3.9, but I need to dig a little more to confirm which (or trial and error). Alternatively, remove the nose test suite and make no guarantees of compatibility with the unmaintained testing library.

@h2non do you have an inclination about which you prefer or any other alternative approaches to take?

[KyleJamesWalker]

This is great if there's any special code for anything below 3.7 I would drop the extra effort for anything that's already EOL

https://endoflife.date/python

[sarayourfriend]

Other than the tox configuration running on versions as low as 3.5 I don't think there are any other version checks or version specific code left.

[KyleJamesWalker]

@h2non Any chance this will be added/reviewed soon?

Note if anyone else needs this while the PR is open I was able to verify it works with my python 3.10 project by simply installing the forked version with:

pip install -U https://github.com/sarayourfriend/pook/archive/refs/heads/fix/async-coroutine-deprecation.zip