Fix "signature verification error" due to expired key

[micahflee]

PGP key servers are the worst.

This error was happening because the public key included in torbrowser-launcher expired, and refreshing keys from the keys.openpgp.org keyserver failed because Tor Project didn't specifically push the new key and verify their email address with that keyserver. And refreshing from SKS keyservers is not an option because the SKS project is permanently broken, and the Tor Browser signing key is spammed with so many fake sigs that you can't download it. (The same thing has happened to my personal key.)

So this PR does away with keyservers altogether and instead updates the PGP key using WKD, fetching the public key from torproject.org, which is what Tor's sig verification documentation now calls for anyway.

It also includes a new, non-expired version of the public key. And fixes another bug, using package version comparison instead of string comparison to compare version numbers, so that "10" is not less than "9".

I'm terribly sorry for ignoring this issue for so long, everyone. If you're trustworthy and want to take over maintenance of this project please contact me at micah@micahflee.com.

Fixes #525, #524, #523, #520, #519, #518, #517, #516, #515, #514, #512, #510, #509, #508, #504, #498, #497, #496, #495, #493, #492, #491, #490, #489, #487, #481, #476, #474, #467, #458, #457, #455, #454, #453, #452, #448, #447, #437, #431, #430, #429, #428, #424, #410, #388, #386, #384, #379

[eli-schwartz]

If you use setuptools instead of distutils, you could add install_requires=["packaging"], to your setup() arguments and thereby guarantee the dependency is installed.