Add medals

* Refactor usage of ````comment```` and ````cheer```` partials. Instead of sending single possible param, now all params should be right in the path (````resource````) with curly brackets.
* Add Medals resource with two endpoints: ````medals/```` for current user (it doesn't have post to cheers) and ````users/:user_id/medals/```` for accessing medals of any user.