* Moved amazon tests to folder
* Abstracted amazon payment code and added initial test
* Abstracted cancel and subscribe logic to amazon payment lib
* Added arg checks to checkout
* Added constants. Added more subscription test
* Added with arg checks to cancel
* Fixed linting issues
* Added integration tests for amazon subscribe cancel
* Added integration test for amazon checkout
* Added integration test for amazon subscribe
* Added coupon unit test
* Fixed lint
* Fixed minor test issue and changed header expectations
* Fixed line endings
