Shopify/active_merchant — pull request #273 by stiak (2012-02-17 00:05:02+00:00)
Title: Add shipping callback setup

This is dependent on #272 being accepted. It adds the setup required to perform instant update callbacks (https://cms.paypal.com/us/cgi-bin/?cmd=_render-content&content_ID=developer/e_howto_api_ECInstantUpdateAPI)