2.4.0

2.4.0

• Issues/add missing fields
• Support upcoming invoices with subscription only
• Warn when unknown objects are processed
• Add missing invoice endpoints
• Add support for sending invoices
• Update Stripe version
• Use Jason over Poison
• Set minimum elixir version to 1.7
• Add support for Subscription Schedules
• Add Stripe Issuing
• Add CreditNote api calls
• Add tax_rate struct and api calls
• Format mix.exs to pass CI
• Reorganize docs
• Add PaymentMethods module, with struct, list/2, attach/2, detach/2