You don't need this source code unless you want to modify the gem. If you just want to use the Stripe Ruby bindings, you should run:
sudo gem install --source https://code.stripe.com stripe
If you want to build the gem from source:
sudo gem build stripe.gemspec
Ruby 1.8.7 or above. (Ruby 1.8.6 may work if you load ActiveSupport.)
The stripe gem is mirrored on Rubygems, so you should be able to install it via gem install stripe if desired. We recommend using the code.stripe.com mirror so all code is fetched over SSL.