User Story 47, Admin visits Merchant Index Page

[iandouglas]

As an admin user
When I visit the merchant's index page at "/merchants"
I see all merchants in the system
Next to each merchant's name I see their city and state
The merchant's name is a link to their Merchant Dashboard at routes such as "/admin/merchants/5"
I see a "disable" button next to any merchants who are not yet disabled
I see an "enable" button next to any merchants whose accounts are disabled

Checklist:

• base code 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 #24

depends on #23