Cluser connect should allow for username/password

Okay so I'm prefacing this with saying that I don't know if this is the ruby way or not, but it feels "not sdk3ish" to have to create options and then call authenticate on the options. I think ruby supports overloads through args* and then maybe it should also allow for the connect(connstr, user, password) string string string overload?

Also, I wonder if instead of authenticate on the options it could take an authenticator which is either a password authenticator or a cert authenticator? The Authenticator interface is defined in the sdk3 bootstrapping rfc.