add artist AR model
add genre AR model
add track AR model
add a track fetcher
add audio_clip_url in saved tracks
seeds for Genres
add game and quiz AR models
add a GameGenerator class
cache only tracks with auidio_clip_url available
fix GameGenerator
add endpoint for creating new games
update db/schema.rb
run migrations on deploy
require 'track' in Quiz to avoid undefined Track
create Game by passed genre or first genre available
rename tracks to quizzes in returned json on game creation
add method to check if answer is correct
add endpoint in api to check if an answer to a quiz is correct
show audio_clip_url only from right answer in quizzes
add thumbnail_url to Track