`querystring` => `qs`, adds support for nested objects

Enables transmitting nested objects with Content-Type `application/x-www-form-urlencoded`.

```bash
curl -XPOST http://localhost:3000/aloha \
-H "Content-Type: application/x-www-form-urlencoded" \
-d '
user[name][first]=Johnny&user[email]=jvdomino@gmail.com
'
```