Support Java 8 Lambda Expression syntax

With this change you can use this slick syntax:

```java
public static SockJSRouter hello = SockJSRouter.whenReady((in, out) -> {
 
    // Log each event received on the socket to the console
    in.onMessage(System.out::println);
 
    // When SockJS connection is closed.
    in.onClose(() -> System.out.println("Disconnected"));
 
    // Send a single 'Hello!' message
    out.write("Hello!");

});
 
 ```