Added Payscout Gateway

Here is the gateway documentation:
https://secure.payscout.com/merchants/resources/integration/integration_portal.php

I have added to this branch:

* Test Credentials
* Remote Tests
* Unit Tests
* Gateway Code

Running Tests:

rake test TEST=test/unit/gateways/payscout_test.rb
rake test TEST=test/remote/gateways/remote_payscout_test.rb