With Stowaway for iPhone 5 ($35), Incipio took the concept of its earlier iPhone 4/4S credit card-holding case and seriously refined it. The new version is much slimmer and cleaner-looking, using a design that matches the rest of the company's iPhone 5 lineup. A single-piece rubber and plastic case snaps around the device offering solid protection, including coverage for the buttons and separated openings for the bottom ports. Pop open the door…