ipn: move state to Webhook object.
Show a status message immediately when user submits credit card.
Stripe gold subscriptions.
Renable submit button on all stripe exceptions.
Don't PM users with gold subscription about expiration.
Don't allow multiple gold subscriptions on an account.
complete_gold_purchase is a classmethod of GoldPaymentController.
Need to use hasattr to check for stripe_customer_id.
CreditGild needs a value for period.
Raise NotFound if full name type is not thing or relation.
GoldSubscription: convert pennies to a float before doing math on it.
CassandraCache: convert 0 time to None ttl.