I'm afraid that this is not possible. If you add virtus here, it will be something like a development dependency ( / it will only be installed if you run `bundle` in the directory of `ashikawa-ar`). If you run `gem install ashikawa-ar` or install it as a dependency via a Gemfile, it won't get installed.
There's no way to add a Gem as a dependency which is just a github repo and not a gem, so we can't add virtus as a dependency as long as its not on Rubygems :crying_cat_face: @solnic, can you maybe create a release candidate?