Fix regexp for detecting command-line options in /bin/pegjs

Closes GH-51.

bin/pegjs

@@ -45,7 +45,7 @@ function abort(message) {
 var args = process.argv.slice(2); // Trim "node" and the script path.
 
 function isOption(arg) {
-  return /-.+/.test(arg);
+  return /^-/.test(arg);
 }
 
 function nextArg() {