Add 'unsubscribe' argument to createUser() and updateUser(). 

Send value for to the 'unsubscribed_from_emails' argument of the Intercom /users API. Enables sync of application user preferences with Intercom (and compliance with anti-spam laws).

See: https://api.intercom.io/docs#creating_a_user
unsubscribed_from_emails: A boolean value representing the users unsubscribed status.