3.4.0

• Latest generated changes for v2019-10-10 #354
  • convert trial endpoint
  • item-backed add-ons
  • IBAN billing info
• Use new webhooks doc link #353
• Updating User-Agent to match standards #352
• Latest v2019-10-10 Changes #350
  • More documentation
  • Account#has_* flag attributes
  • Gateway Token Support
• Add missing RateLimitedError #346