Move exports identifier from UMD template to commonArgs

lib/6to5/transformation/modules/umd.js

@@ -38,7 +38,7 @@ UMDFormatter.prototype.transform = function (ast) {
   defineArgs = defineArgs.concat(names);
   defineArgs = [t.arrayExpression(defineArgs)];
 
-  var commonArgs = [];
+  var commonArgs = [t.identifier("exports")];
   if (this.passModuleArg) commonArgs.push(t.identifier("module"));
   commonArgs = commonArgs.concat(names.map(function (name) {
     return t.callExpression(t.identifier("require"), [name]);

lib/6to5/transformation/templates/umd-runner-body.js

@@ -2,6 +2,6 @@
   if (typeof define === "function" && define.amd) {
     define(AMD_ARGUMENTS, factory);
   } else if (typeof exports !== "undefined") {
-    factory(exports, COMMON_ARGUMENTS);
+    factory(COMMON_ARGUMENTS);
   }
 });