<Client> has missing properties

[fabriziomoscon]

ref:
https://www.twilio.com/docs/api/twiml/client#examples-3

this should be possible:

twiml.ClientOpts{
	StatusCallbackEvent:  "initiated ringing answered completed",
	StatusCallback:       "https://myserver.com/connect/",
	StatusCallbackMethod: "POST",
}

but those field are missing from the struct.

Would you accept a PR with a fix?