* Added unified message to ErrorResult
* Added ability to specify country using country_name, country_code_alpha2, country_code_alpha3, or country_code_numeric (see [ISO_3166-1](https://en.wikipedia.org/wiki/ISO_3166-1))
* Renamed Subscription retryCharge to retry_charge
* Added gateway_rejection_reason to Transaction and Verification
* Allow searching with date objects (in addition to datetime)
* When creating a Subscription, return failed transaction on the ErrorResult if the initial transaction is not successful