ghi shouldn't prompt for your password

It's bad practice to teach users to enter their passwords into random places; I'd really love to see ghi set a stronger security bar.

There are probably a few different ways to not prompt for passwords (including becoming a full-fledged Oauth client); here's one that works right now, and could be implemented just with a documentation fix:

Go to https://github.com/settings/tokens and generate a personal access token, give it repo perms, then run git config --global ghi.token <that token>.