Braintree

* Add configuration option for custom HTTP strategies

* Adds hold_in_escrow method
* Add error codes for verification not supported error
* Add company_name and tax_id to merchant account create
* Adds cancel_release methods
* Adds release_from_escrow functionality
* Adds owner_phone to merchant account signature.
* Adds merchant account phone error code.

* Adds device data to transactions, customers, and credit cards.

* Adds disbursement details to transactions.
* Adds image_url to transactions.

* Support requests >= 1.0
* Add new validation errors and rename old ones

* Adds channel field to transactions.