Can't add a URL to makeCall?

[alexandraclark]

Thanks for all your work on this package! It's been very useful.

As far as I can tell, there's no field for adding a TwiML URL in the makeCall function. I get this error when trying to call with just the "to" parameter:

Exception in callback of async function: { status: 400,
message: 'Url parameter is required. For more information, see http://www.twilio.com/docs/api/twiml', code: 21205,
moreInfo: 'https://www.twilio.com/docs/errors/21205' }