Add #item_messages and #item_errors? to Suretax::Api::Response.  Add Suretax::Api::ItemMessage to encapsulate item messages.
Add Suretax::Api::CancelRequest to encapsulate issuing a cancel request
Merge pull request #28 from bqsoft/add-response-item-messages

Add CancelRequest class and extend Response with #item_messages and #item_errors?