In-browser SIP phone

In-browser SIP phone that uses the [ctxSip phone](https://github.com/collecttix/ctxSip). Starts automatically on load, and events can be subscribed to and calls made programmatically from Kazoo UI (via winkstart.publish).

I can understand that this may not be the sort of thing that you want in the base repository, but if there's any feedback or any suggestions for improvement please let me know.

Cheers,
Sam