OK, looking at this I decided that I didn't like how I solved the additional files thing. I'm reworking that part of the API.

Currently the `additional_files` bit is not in use -- it was added to support languages like Scala that have a different directory structure than the simplistic assumptions that I made originally here.

I'm going to rework it to return all the files in a hash that is structured so that it will be simple to unmarshal it into a proper struct on the CLI side of things. I'll still return the old test_file as well, since we need to be backwards compatible.