Support OAuth for GitHub

[notpushkin]

Since logging in using password is just uncool. Also, two-factor auth isn't supported when logging in with HTTP auth.

Possible things to do:

• Personal access tokens
• Real OAuth flow, e. g. via hello.js (a bit harder, but friendlier)

[gmaclennan]

You can already use personal access tokens as described in the README. Personal access tokens will work for two-factor.

[notpushkin]

Oh, sorry! Wrong repo. I'm so disorganized. This issue was meant for some other project using this library, I just mixed two tabs up.