Update to match docs (#67)

* [breaking] Rename create_intent -> create_payment_intent. Clients shouldnt pass amount

* Use keyword arguments for readability

* Authenticate in create_payment_intent

* Use default arguments in create_payment_intent

* Refactor out create_and_capture_payment

* [breaking] Combine capture_payment and confirm_payment endpoint into confirm_payment, like the docs recommend.

* Organize methods

* Remove payment_method_types, it should always be 'card' (the default).  card_present is not relevant for this backend

* [breaking] Dont pass amount

* Add source_id params to create_payment_intent so its parity with manual version

* Move Setup Intent endpoint down too

* Add PI webhook

* Comment hardcoded amount

* Rename manual PI endpoint to /confirm_payment_intent

* fix

* Refactor out create_payment_intent

* Add customer_id to create_payment_intent, for Standard Integration.

* [breaking] payment_method -> payment_method_id

Also, use_stripe_sdk comment, finish refactoring out create_payment_intent

* Dont pass currency from client either!

* Add emoji to the iOS Backend (#68)

* Add emoji store products to backend

* Add 3063 (3ds1 required) card

* Always calculate_price, fix up default ending up being overwritten to 0

Author: yuki-stripe