Add homepage or source code URI to rubygems.org

[nirvdrum]

The metadata for the futuroscope gem on RubyGems is a bit lacking. Since neither the homepage nor the source code URI values are set on rubygems.org, there's no easy way to correlated this repo with the gem. I did it by cross-referencing the release tags to the versions listed on rubygems.org.

If someone with permissions could add the missing values on rubygems.org, that would be much appreciated.