add play model.
fix migration error and regenearte play model.
Merge pull request #29 from yuchan/yo-store-data-of-play-quiz

add play model
judging users_s answer is correct.
Merge pull request #30 from harakoji/master

judging users_s answer is correct.
add rubocop
add settings
add rubocop
fix Gemfile.lock
resolve conflicts