This moves the Postmark PHP library out of this module and into the sites/all/libraries folder, using the Libraries module to handle the integration. The Libraries module must be version 2.0 or higher.
NOTE: The Drupal 7 version of the Postmark module requires installation of the Mail System module. The Mail System module allows you to switch between mail handlers, and can also define different mail handlers on a module by module basis. This can be used with the core Contact module, for example, if you don't like how Postmark handles it as described below.