Refactor setupEntries and export route

Refactor setupEntries

Export route to use middleware like this
```
    var myapp = express();
    myapp.use(stubcell.route);
    var server = myapp.listen(9000);
```

Require merge [stubrec](https://github.com/yosuke-furukawa/stubrec/pull/1)
Is it necessary for only a api `setHeaders`?