Support bundler

When using the `git:` option in a Gemfile bundler will look for a folder with the same name as the gem if the gemspec cannot be found in the root.

I also like to mention that having separate repositories for every implementation is much saner. For example:

- https://github.com/koraktor/steam-condenser-ruby
- https://github.com/koraktor/steam-condenser-php