fix bug in #33

Author: mengyuan.ymy

index.js

@@ -106,7 +106,7 @@ function expand(str, isTop) {
   var isNumericSequence = /^-?\d+\.\.-?\d+(?:\.\.-?\d+)?$/.test(m.body);
   var isAlphaSequence = /^[a-zA-Z]\.\.[a-zA-Z](?:\.\.-?\d+)?$/.test(m.body);
   var isSequence = isNumericSequence || isAlphaSequence;
-  var isOptions = /^(.*,)+(.+)?$/.test(m.body);
+  var isOptions = m.body.indexOf(',') >= 0;
   if (!isSequence && !isOptions) {
     // {a},b}
     if (m.post.match(/,.*\}/)) {