New formula: git-hub

git-hub is a git plugin for interacting with GitHub's REST API.
https://github.com/ingydotnet/git-hub
Again, can this test be modified to do something more substantial then e.g. `--version` or `--help`? See `cmake.rb` for an example of an application formula with a good test and `tinyxml2.rb` for an example of a library formula with a good test. Thanks!