Added `pass` method to pipeline variables into Javascript

You can pipeline server-side information into client-side Javascript variables using the `pass` method:

    $this->assets->pass([
            'route' => [
                'name'       => Route::name($this->request->route()),
                'controller' => strtolower($this->request->controller()),
                'action'     => $this->request->action()
            ],
            'url' => [
                'base'  => URL::base(),
                'media' => URL::base().Media::uri('/').'/'
            ],
            'environment' => Kohana::$environment
        ]);

When you use `Assets::get()` to retrieve all the `head` assets, data will be encoded like this:

    <script type="text/javascript">window.pass = { "route": { "name": "default", "controller": "Welcome", "action": "index" }, "url": { "base": "/", "media": "/media/kohana/" }, "environment": 40 };</script>

In Javascript, your variables are set and ready to use within the `window.pass` global variable.