core: Add devise gem
frontend: Add routes for devise
core: Implement configuration
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
core: Improve mail subject at order completion
core: Decompose the method for order completion with exception or no
core: Remove messages on order invalid exception
frontend: Remove to rescue ActiveRecord::RecordInvalid
core: Change timing to save stocks quantity decrement
frontend: Fix order flow for signed-in customer
core: Install jquery-rails for suppport signout with DELETE method
frontend: Add login and logout menu for members
core: Install enumerize gem
core: Initialize comable addresses