User Story 27, User cancels an order

[megstang]

As a registered user
When I visit an order's show page
I see a button or link to cancel the order only if the order is still pending
When I click the cancel button for an order, the following happens:
- Each row in the "order items" table is given a status of "unfulfilled"
- The order itself is given a status of "cancelled"
- Any item quantities in the order that were previously fulfilled have their quantities returned to their respective merchant's inventory for that item.
- I am returned to my profile page
- I see a flash message telling me the order is now cancelled
- And I see that this order now has an updated status of "cancelled"

DO THESE STORIES FIRST:

• User Story 18, User Profile Show Page
• User Story 26, User views an Order Show 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-examples#222

child of turingschool-examples#242

depends on turingschool-examples#220

depends on turingschool-examples#212