End of Chapter 10

Change-Id: I8f9452c041af02516fcb01b6f08b8bc568eb6c6a
chapter 10 questions finished

Change-Id: I4a0d070cfcbdf841cf5b81ef441fc2bef861a797
Merge branch 'master' of github.com:joeytall/Agile-Development-with-Rails-4

Conflicts:
	app/controllers/carts_controller.rb
	app/models/line_item.rb
	app/views/carts/show.html.erb

Change-Id: I7b921fd763b78f0f291ed4bc96099b010687c99f