Display --help message if run without arguments

Fixes #389

core/modules/startup.js

@@ -223,8 +223,12 @@ exports.startup = function() {
 		});
 	} else {
 		// On the server, start a commander with the command line arguments
+		var args = $tw.boot.argv;
+		if(args.length === 0) {
+			args = ["--help"];
+		}
 		commander = new $tw.Commander(
-			$tw.boot.argv,
+			args,
 			function(err) {
 				if(err) {
 					console.log("Error: " + err);