Fix broken remote tests due to changes to the test servers on Merchant Ware's side.
Use MerchantWare's v4 api for voiding transactions. Allows for voiding authorizations without first capturing them.
Fix syntax error for ruby < 1.9
Coding style fixups.
Merge pull request #557 from Shopify/merchantware-void-update

Fix transaction voiding issues with MerchantWare integration.