Add "How to login with Access Token" in FAQ

[jedie]

IMHO it's a good idea to add a quick Howto generate and use the access token in the FAQ.

With the information that https://github.com/settings/tokens is under:
Settings / Developer settings / Personal access tokens

Maybe link also to: https://blog.github.com/2013-05-16-personal-api-tokens/

This may fix issues like #1770

[casperklein]

A recommendation about which scopes to allow for the personal access token would also be helpful.