tox-to-nox: support descriptions

[ktbarrett]

Closes #574. I didn't see any tox-to-nox tests, but it's a small enough change to manually confirm.

[FollowTheProcess]

There are tox-to-nox tests in tests/test_tox_to_nox.py they're all fairly simple "tox file in, nox file out" type tests, should be easy enough. If we're going to merge this in we'd need a test please, otherwise this looks great 👍🏻

Edit: I've never actually used tox, can envname.description be a multi line string? If so we'd probably want to handle stripping extra whitespace etc.

[ktbarrett]

tox allows multiline string and folds them into a single line.

[FollowTheProcess]

tox allows multiline string and folds them into a single line.

Cool! thanks

[FollowTheProcess]

@ktbarrett when you get a sec can you resolve the conflicts on this (it's just conflicting with your other change) and then we can get it merged in 👍🏻

[FollowTheProcess]

Thanks @ktbarrett 🎉