Application#condition now handles status code and callback arguments cor...

...rectly.

If you do this `condition(statusCode, cb)`, as in the README examples:

    .condition(401, function (req, resp, cb) {
      req.on('condition.auth', function (e, user) {
        if (req.user.id !== req.routes.params.userid) return cb('You can only access your own user document.')
        cb(null, user)
      })
    })

The 401 status code is ignored and 500 gets sent instead.

This commit corrects that.
Not completely happy about the logic, but it works.