Ginkgo convert

Usage: `ginkgo convert path/to/package` 

This command reads in the testfiles in the given package and rewrites the XUnit style tests as (incredibly naive) Ginkgo tests.

I thought about naming the command `ginkgo transmogrify`, in order to give it a bit more flair and indicate to users that there's some strange, deep magick at work here, but ultimately decided against it.

![transmogrify](https://lh3.ggpht.com/-7i5m5GysnnY/TcC6btifnPI/AAAAAAAAAKg/_faHnUFUSeM/s1600/Picture3.png)

Currently the only tests for this are integration tests that take real fixtures, shell out to `ginkgo convert` and compare the converted files to some goldmaster files.