koajs/route — pull request #14 by navaru (2014-05-02 07:01:26+00:00)
Title: Fix: make null the unmatched optional parameter

Fixes the following:
```
route.get('/:resource/:id?', function (resource, id) {
// resource === 'users'
// id === 'undefined' <-- a string
}}

request.get('/users')
```