gem_home 0.1.0 (new formula)

This is the formula for [gem_home](https://github.com/postmodern/gem_home).
Can a test be added to do something more substantial than 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!