Support for Secure Token, Transparent Redirect

[davidlmontgomery]

It appears this library provides no support for Secure Token and Transparent Redirect (i.e., parameters SECURETOKENID, CREATESECURETOKEN, and SILENTTRAN).

Classes/Fields for these can easily be added and passed as 'extras', but routines like PayflowProClient.authorization require credit_card, which must not be sent for Secure Token calls -- the whole idea is that the server code never sees the credit_card.

[bkeating]

Thank you for taking the time to post this. Im no longer using this project or have time to develop it further, but I can commit some time to review code and tinkering with it locally if you'd like to submit a pull request (or anyone else who is listening in here).