Move address into transport config

This makes it possible to use a factory function to create a transport of the right type and not having to repeat the address when calling Transport.Connect()

_examples/xmpp_component/xmpp_component.go

@@ -10,9 +10,11 @@ import (
 
 func main() {
 	opts := xmpp.ComponentOptions{
+		TransportConfiguration: xmpp.TransportConfiguration{
+			Address: "localhost:8888",
+		},
 		Domain:   "service2.localhost",
 		Secret:   "mypass",
-		Address:  "localhost:8888",
 		Name:     "Test Component",
 		Category: "gateway",
 		Type:     "service",