py-braintree: updated to 4.2.0

4.2.0

Add retrieval_reference_number to Transaction
Add network_transaction_id to CreditCardVerification
Add product_sku to Transaction
Add customer_device_id, customer_location_zip, and customer_tenure to RiskData
Add phone_number and shipping_method to Address
Add validation error codes:
  Transaction.ShippingMethodIsInvalid
  Transaction.ShippingPhoneNumberIsInvalid
  Transaction.BillingPhoneNumberIsInvalid
  RiskData.CustomerBrowserIsTooLong
  RiskData.CustomerDeviceIdIsTooLong
  RiskData.CustomerLocationZipInvalidCharacters
  RiskData.CustomerLocationZipIsInvalid
  RiskData.CustomerLocationZipIsTooLong
  RiskData.CustomerTenureIsTooLong

(adam)