This code is an example of how to transfer a call using Twilio. It has been written for the following very specific scenario only:
An agent, using Twilio Client calls a customer. The agent wants to transfer the customer to a colleague so presses the "Transfer" button on the Client. This puts the customer on hold and connects the agent to the colleague. After a brief chat, the colleague agrees to talk to the customer so the agent presses "Transfer" again. The agent, customer and colleague are all, now, in a three way call. The agent completes the transfer by hanging up.
Over time, I plan to increase the complexity, and real world applicability, of this demo by allowing for multiple client connections and multiple concurrent calls. I'm sure my plans will solidify as I work on them.