Add cukes from https://github.com/github/hub/pull/738
Improve auth process

This is to follow implementation in https://github.com/github/hub/pull/738
Start counting auth token note from 1
Fix enterprise authentication cuke and move it to authentication.feature
Bump Octokit for error parsing fix

Brings in octokit/go-octokit#73
Avoid showing warning about invalid 2FA code on first prompt
Merge pull request #743 from github/imporve_auth_process

Improve authentication process for v2.2.0

Fixes #728, fixes #622