Improve the CLI auth logic

[ankon]

These are changes I needed for creating a desktop application using this library:

1. Provide client_id, client_secret, note, note_url, and fingerprint in the authorization request
2. Allow reusing an existing authorization

There is still one open issue here: github will return a hashed token and the last 8 characters when reusing a token, but these values are not provided to the callback, so the app cannot actually verify the token. I'll open a separate issue for that, as it might need incompatible changes to the API.

[pksunkara]

Just a few comments which need to be addressed.

[pksunkara]

@ankon Any update on this?

[pksunkara]

@ankon Could you give an update on this?

[ankon]

Oops, missed this. :/

I'm no longer using this library, so right now can not do any updates.