Made res available in user.use(req, res)

Hello,

This is a small update to make ```res``` available in ```user.use(req, res)```. My use case is to add a function to res like this:

```
var filter = require('json-schema-filter');
var fs = require('fs');
var highland = require('highland');

user.use('access private page', function (req, res) {
  if (req.user.role === 'moderator') {
    var moderatorFilter = highland.curry(filter, JSON.parse(fs.readFileSync('./authorization-schemas/moderator.json', {encoding: 'utf8'})));
    res.jsonAuthorized = highland.compose(res.json, moderatorFilter);
    return true;
  }
});
```