username and password parameters
_edit: reading comprehension issues:  should have read example again. Can close_

I noticed you are using the node req/res objects here:

`var res = yield auth.bind(auth, this.req, this.res)`

How is this working with the passport local strategy? The req.query and req.body parameters aren't defined normally (`this.req.query`) but `this.request.query` should be defined. The passport local strategy checks in `Strategy.prototype.authenticate = function(req, options)`

``` js
Strategy.prototype.authenticate = function(req, options) {
  options = options || {};
  var username = lookup(req.body, this._usernameField) || lookup(req.query, this._usernameField);
  var password = lookup(req.body, this._passwordField) || lookup(req.query, this._passwordField);
```
