User Story 54, Merchant cannot fulfill an order due to lack of inventory

[BrianZanti]

As a merchant
When I visit an order show page from my dashboard
For each item of mine in the order
If the user's desired quantity is greater than my current inventory quantity for that item
Then I do not see a "fulfill" button or link
Instead I see a big red notice next to the item indicating I cannot fulfill this item

DO THESE STORIES FIRST:

• User Story 52, Merchant sees 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 #212

child of #274

depends on #211