Make "Event" class publish

In order to create custom serialization code (using `JsonSupport`) I
need to be able to create `Event` classes

src/main/java/com/corundumstudio/socketio/protocol/Event.java

@@ -17,7 +17,7 @@ package com.corundumstudio.socketio.protocol;
 
 import java.util.List;
 
-class Event {
+public class Event {
 
     private String name;
     private List<Object> args;