Added default implementation of stop() function.

modules/node_modules/node_helper/index.js

@@ -23,6 +23,17 @@ NodeHelper = Class.extend({
 		console.log("Starting module helper: " + this.name);
 	},
 
+	/* stop()
+	 * Called when the MagicMirror server receives a `SIGINT` 
+	 * Close any open connections, stop any sub-processes and 
+	 * gracefully exit the module.
+	 *
+	 */
+	stop: function() {
+		console.log("Stopping module helper: " + this.name);
+	},
+
+
 	/* socketNotificationReceived(notification, payload)
 	 * This method is called when a socket notification arrives.
 	 *