Google Groups whitelist and admin group

[missingcharacter]

in jupyterhub_config.py add the lines below:

c.GoogleOAuthenticator.google_group_whitelist = { 'someGSuiteGroup' }
c.GoogleOAuthenticator.admin_google_groups = {'gSuiteGroupWhoseMembersShouldBeAdmins'}
c.GoogleOAuthenticator.scope = ['openid', 'email', 'https://www.googleapis.com/auth/admin.directory.group.readonly']

I have to admit I made the changes to make it work, but this is not pretty, let me know if there is something you'd like me to change.

[missingcharacter]

I can also update docs once #336 is merged

[missingcharacter]

closing since this requires a service account