Api 179 add tracking headers

It looks like RUBY_PLATFORM is available, and if we want uname we can get it for linux and mac os: https://github.com/stripe/stripe-ruby/blob/afd42ecd416554d5c2493498aebe03cbfd9d7d68/lib/stripe.rb#L156-L175

I'm happy to use the same approach in clever-go and clever-js