correctly normalize json path

in the case where you make a relative require w/ a `..` in the path:

```js
require([
    'json!./../string-bundle.json'
], function(strings) {
    // ...
});
```

the plugin's `normalize` function needs to call the supplied `normalize` parameter (i.e. [the second argument](http://requirejs.org/docs/plugins.html#apinormalize) to the plugin's `normalize` function) in order to correctly resolve the `..`.