Add medals and top sports

* 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.
* Add TopSport resource with two endpoints: ````top_sports/```` for current user and ````users/:user_id/top_sports/```` for accessing sports of any user.