Update readme - add options to useExpressServer

Author: 19majkel94

README.md

@@ -295,7 +295,9 @@ import {useExpressServer} from "routing-controllers";
 let express = require("express"); // or you can import it if you have installed typings
 let app = express(); // your created express server
 // app.use() // you can configure it the way you want
-useExpressServer(app); // register created express server in routing-controllers
+useExpressServer(app, { // register created express server in routing-controllers
+    controllers: [UserController] // and configure it the way you need (controllers, validation, etc.)
+});
 app.listen(3000); // run your express server
 ```