Add note about upgrading pip

[Gerardwx]

No description provided.

[bhrutledge]

Thanks for this!

Also: hello! If you don't mind, I'm curious what prompted you to set up a dev environment for Twine. :) Are you thinking about contributing?

[Gerardwx]

bhrutledge,
Sorry for delay. I was looking into the issue where uploads hang due to linux keyring. I got as far as realizing keyring was executing code on import and then having to time out waiting for something -- dbus, I think. I realized I had just installed a couple keyring packages on my development machine I ended up deciding not to use. Removing the packages solve the hanging problem for me.