Added skeleton for client side of subscription

parser/src/test/java/org/dna/mqtt/moquette/server/ServerIntegrationTest.java

@@ -3,6 +3,7 @@ package org.dna.mqtt.moquette.server;
 import java.io.IOException;
 import org.apache.mina.core.service.IoConnector;
 import org.dna.mqtt.moquette.client.Client;
+import org.dna.mqtt.moquette.client.IPublishCallback;
 import org.junit.Test;
 
 /**
@@ -24,7 +25,12 @@ public class ServerIntegrationTest {
         client.connect();
         
         client.publish("/topic", "Test my payload".getBytes());
-        //TODO client.subscribe("/topic", callback)
+        client.subscribe("/topic", new IPublishCallback() {
+
+            public void published(String topic, byte[] message) {
+                throw new UnsupportedOperationException("Not supported yet.");
+            }
+        });
         
         client.close();
     }