Added documentation for ddp.close()

Author: vsivsi

README.markdown

@@ -108,6 +108,12 @@ ddpclient.on('message', function (msg) {
   console.log("ddp message: " + msg);
 });
 
+/*
+ * Close the ddp connection. This will close the socket, removing it
+ * from the event-loop, allowing your application to terminate gracefully
+ */
+ddpclient.close()
+
 /*
  * If you need to do something specific on close or errors.
  * You can also disable auto_reconnect and