Bug 1062805 - Used the shared JSON file load helper in the ringtones app R=Goutam

The ringtones app doesn't use require.js, you'll need to add the dependency inside the index.html like it's done in other apps, e.g.:

https://github.com/mozilla-b2g/gaia/blob/daf59bcc29fdd80901a4d6bd94191f7f06be8c4b/apps/sms/index.html#L47