Show all orders

Previously, there was no way to view all orders at the same time, which
was causing an issue when an administrator wanted to easily see what
customers had been ordering. A list of orders has been added that links
off to each individual order page.

https://trello.com/c/DwAdkFpQ
Restrict access to order screens
Refactoring some things
Add Stripe integration
Remove Stripe exception handling

Previously, an exception was being caught when the Stripe API returned
an error, which has not been scoped into the project yet. The exception
block has been removed from the Order controller's create action.
Add Stripe keys to test environment
Use the Travis config from suspenders
Remove test variables
Fix typo in Travis config