Added PublisherListener example to documentation.

docs/src/main/sphinx/advanced.rst

 Advanced topics
 ===============
 
+Listeners
+---------
+
+Because rosjava provides a primarily asynchronous API, many classes which allow
+you to provide event listeners. For example,
+:javadoc:`org.ros.node.topic.PublisherListener`\s allow you to react to
+lifecycle events of a :javadoc:`org.ros.node.topic.Publisher`. The snippet
+below adds a :javadoc:`org.ros.node.topic.PublisherListener` that will log a
+warning message if the :javadoc:`org.ros.node.topic.Publisher` fails to
+register with the master. ::
+
+  Node node;
+  Publisher<std_msgs.String> publisher;
+
+  ...
+
+  publisher.addListener(new DefaultPublisherListener() {
+    @Override
+    public void onMasterRegistrationFailure(Publisher<std_msgs.String> registrant) {
+      node.getLog().warn("Publisher failed to register: " + registrant);
+    }
+  });
+
 Messages as BLOBs
 -----------------
 
@@ -20,4 +43,3 @@ little endian. ::
       .newMessageDeserializer(sensor_msgs.PointCloud._TYPE)
           .deserialize(buffer);
 
-