User Story 16, Item Show Page

[memcmahon]

As any kind of user on the system
When I visit an item's show page from the items catalog
My URI route is something like "/items/18"
I see all information for this item, including:
- the name of the item
- the description of the item
- a larger image of the item
- the merchant name who sells the item
- how many of the item the merchant has in stock
- the merchant's current price for the item
- an average amount of time it takes this merchant to fulfill this item

If I am a visitor or regular user, I also see a link to add this item to my cart

DO THESE STORIES FIRST:

• User Story 14, Items Index Page

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#257

child of turingschool-projects#274

depends on turingschool-projects#256