Added cart build for user in MainController. Added product add to cart showing condition on main/index. Added :dependent => :destroy in Cart and User
Changed build_cart to create_cart in MainController
Added :uniq => true into Cart products association
Added flash messages show in application.html.erb
Created CartsController and added add_to_cart function to Main#index
Moved build_user_cart into ApplicationController. Created CartsController#index
Created carts/index.html.haml. Created header partial. Added carts/index into routes.rb
Updated schema