Add the ability to send CreditCard e-mail via Auth/Capture API calls.

This one is pretty self explanatory. E-mail is provided to CreditCard, but those details aren't passed along to `TransactionAPI.auth` or `TransactionAPI.capture`. This fixes that.

Otherwise, for some CC types, this error is raised:
```AuthorizeResponseError: Email is required. full_response={'cvv_response': '', 'authorization_code': '', 'response_code': '3', 'amount': '1.20', 'transaction_type': 'auth_only', 'avs_response': 'P', 'response_reason_code': '33', 'response_reason_text': 'Email is required.', 'transaction_id': '0'}```