Adds conditional support for falling back to XCTest-style names of tests.

I use a [tool](https://github.com/AshFurrow/second_curtain/issues/18) that parses the output of test runs in order to do some things with artefacts of that run. This parsing relies on xcodebuild to output the test names in the format native to XCTest. 

Wasn't sure how to approach this one, so I used something borrowed from [Expecta](https://github.com/specta/expecta/blob/7d287afd31166a77b99d3f16a84064166df53ee9/src/Expecta.h#L14-L16). I'm open to alternatives and suggestions on documentation.