Admin Merchant Update

[BrianZanti]

As an admin,
When I visit a merchant's admin show page
Then I see a link to update the merchant's information.
When I click the link
Then I am taken to a page to edit this merchant
And I see a form filled in with the existing merchant attribute information
When I update the information in the form and I click ‘submit’
Then I am redirected back to the merchant's admin show page where I see the updated information
And I see a flash message stating that the information has been successfully updated.