Default host and port can be customized by using methods on RestExtension class.
@Extension		
public RestExtension extension = new RestExtension().host("127.0.0.1").port(9876);
		
		When you run following fixture:
		<rest:request> <rest:get>/hello</rest:get> </rest:request>Then GET request to
/hello has been sent
		to http://127.0.0.1:9876/hello