fix query parameter nesting

the module is currently using the built in `querystring` module which does not do nested query parsing.

This pull request changes it to use the [`qs` module](https://github.com/visionmedia/node-querystring) which is what is used [internally by express](https://github.com/strongloop/express/blob/b08d4441a4804ed332023efb28a6d3d9b6d902cc/lib/middleware/query.js#L6) so that nested query parsing works again