typo fix

index.js

@@ -2,7 +2,7 @@
 
 module.exports = require('greenlock-express');
 module.exports._greenlockExpressCreate = module.exports.create;
-module.create = function (opts) {
+module.exports.create = function (opts) {
   opts._communityPackage = opts._communityPackage || 'greenlock-koa';
   return module.exports._greenlockExpressCreate(opts);
 };