py-braintree: updated to 3.39.0

3.39.0

Add support for upgrading a PayPal future payment refresh token to a billing agreement
Fix braintree.Dispute.search to take a list of search criteria
Add logic to remove deprecation warnings for encodestring and decodestring when used with python 3
Fix spec to expect PayPal transaction to settle immediately after successful capture
Add GrantedPaymentInstrumentUpdate webhook support
Add ability to create a transaction from a shared nonce
Add options -> paypal -> shipping for creating & updating customers as well as creating payment methods
Do not convert to Decimal if amount is None in AuthorizationAdjustement
Add device_data_captured field to risk_data
Add bin_data to payment_method_nonce

(adam)