Merge pull request #29 from bqsoft/constants

Added Suretax constants.
Allow support #submit and #rollback on Suretax::Api::Request and #submit on CancelRequest.

Fix validation checking in Request#submit.

Extract a #valid? method.
Merge pull request #30 from bqsoft/request-wraps-connection

Support #submit for Request and CancelRequest
Adjust names of Suretax constants.