User Story 2, Visitor Navigation

[memcmahon]

As a visitor
I see a navigation bar
This navigation bar includes links for the following:
- a link to return to the welcome / home page of the application ("/")
- a link to browse all items for sale ("/items")
- a link to see all merchants ("/merchants")
- a link to my shopping cart ("/cart")
- a link to log in ("/login")
- a link to the user registration page ("/register")

Next to the shopping cart link I see a count of the items in my cart

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#272

child of turingschool-projects#274