Added function to namespace which checks if namespace is empty

src/main/java/com/corundumstudio/socketio/namespace/Namespace.java

@@ -244,4 +244,9 @@ public class Namespace implements SocketIONamespace {
         return clients;
     }
     
+    // Utility function to check if there are anymore clients in namespace
+    public boolean isEmpty(){
+    	return allClients.isEmpty();
+    }
+
 }