User Story 21, User views their cart show page with items in the cart

[BrianZanti]

As a visitor or registered user
When I have added items to my cart
And I visit my cart ("/cart")
I see all items I've added to my cart
And I see a link to empty my cart
Each item in my cart shows the following information:
- the name of the item
- a very small thumbnail image of the item
- the merchant I'm buying this item from
- the price of the item
- my desired quantity of the item
- a subtotal (price multiplied by quantity)

I also see a grand total of what everything in my cart will cost

DO THESE STORIES FIRST:

• User Story 2, Visitor Navigation

Checklist:

• base tests are written
• base code is written to pass tests
• edge case ("sad path") tests written (if required)
• edge case code written (if required)
• code is reviewed
• branch is merged
• all tests still pass

child of turingschool-projects#249

child of turingschool-projects#274

depends on turingschool-projects#271