Rename git-remote-gitifyhg

Travis-CI doesn't like git-remote-gitifyhg (probably due to path issues).
Rename it to git-remote-testgitifyhg so it shouldn't interfere with anything.
That's also nice because it separates production and development, ensuring
the development version only gets run when it's wanted (one has to have a
remote called "testgitifyhg::mercurial/repo").