fix https://github.com/kataras/iris/issues/683#issuecomment-317229068

Former-commit-id: a42c54708297e6fed78d6fdc2b7cd5ee91c9574b

core/router/handler.go

@@ -114,6 +114,9 @@ func (h *routerHandler) Build(provider RoutesProvider) error {
 	rp := errors.NewReporter()
 
 	for _, r := range registeredRoutes {
+		// build the r.Handlers based on begin and done handlers, if any.
+		r.BuildHandlers()
+
 		if r.Subdomain != "" {
 			h.hosts = true
 		}