Direct-sdk-python2

The SDK has been updated to match version 2.20.3 of the Direct API.

* Updated the SDK to match version 2.11.1 of the Direct API.
** The Payouts.create_payout API method can now throw a DeclinedPayoutException.
* Fixed the API reference URL.
* Fixed an issue with integration tests when no API endpoint port is defined in an environment variable.

Reverted the rename of `errors` init params, field, and method of `ApiException` and all its descendants, except for `DeclinedPaymentException` and `DeclinedRefundException`.

* Payouts have been enabled for webhook events.
* The masking of fields in logging has been updated:
* Masked fields now indicate the length of the value and no longer contain actual data (eg. { "expiryDate": "**30" } is now masked as { "expiryDate": "*4" }).
* Sensitive fields are obfuscated with "***".
* Additional privacy-related fields will now be masked (i.e. "cardholderName", "firstName", "street", and "emailAddress").
* The value of the configuration key "direct.api.authorizationType" can now be in any casing (this means that specifying "v1hmac" is equivalent to "v1HMAC").
* DefaultAuthenticator now only accepts "v1HMAC" (regardless of casing) as value for its authorization_type init parameter.
* ApiException and all its descendants have their `errors` init params, field, and method renamed to `error_response`.

Initial release.