Shopify/active_shipping — pull request #177 by nsimmons (2014-08-07 20:30:20+00:00)
Title: Handle fedex nil response status node

Was seeing some exceptions where `response_status_node(document)` was nil. Not sure what the XML response actually looked like, but we should not assume it contains a 'Notifications' element.

If the response node is not found, we return gracefully.

@garethson @BlakeMesdag