Favorite

@sgharms @linkblaine 

Hey guys, hoping you can help me.
I'm trying to get a functioning "favorite" button to favorite the current track to a user's soundcloud account.
It seems like it should work, aside from the apparently incorrect redirect-uri in the initialize script in layout.html.

The soundcloud API instructed to make a callback.html file, which I did, and to use that as the redirect-uri.  Maggie says the redirect-uri should be localhost:3000/soundcloud-callback.  I don't know how to make this work.  I registered 'http://localhost:3000/callback as the app's redirect-uri on soundcloud api.

Thanks!