Feature/incoming refer (#76)

* Dial: handle incoming REFER on either leg by calling referHook, if configured

* lint

* modify payload of referHook

* support target.trunk on rest createCall api

* bugfix: gather partial result hook was not working

* lint

* handling of incoming REFER

lib/session/confirm-call-session.js

@@ -30,6 +30,10 @@ class ConfirmCallSession extends CallSession {
   _clearResources() {
   }
 
+  _callerHungup() {
+  }
+
+
 }
 
 module.exports = ConfirmCallSession;