rubocop: Refactor methods at the carts controller
FactoryGirl: ignore => transient
rubocop: Refactor methods at the cart owner
rubocop: Refactor methods at the order model
rubocop: Refactor methods at the orders controller
Remove unnecessary methods
Merge pull request #38 from hyoshida/feature/refactor_for_rubocop

rubocop: Refactor codes