:credit_card: Native elixir client for Braintree
[Braintree.Webhook] Allow passing options to webhook parser/validator, similar to other API functions.
[Braintree.Plan] Expand plan functionality with delete, improved guard clauses, and better response code formatting.
[Braintree.Customer] Support ACH Direct Debit payment methods.
[Braintree.HTTP] Fix error in response type specification.
This typespec error wasn't caught given the current dialyzer settings, but could cause issues for clients expecting things like {:error, :not_found}.