There's a case statement in Service#call that uses a syntax that Ruby 1.9 doesn't support:

  response = case @method
             when :post: http.post(@action, "#{@field}=#{CGI.escape(url)}")
             when :get: http.get("#{@action}?#{@field}=#{CGI.escape(url)}")
             end

should be

  response = case @method
             when :post then http.post(@action, "#{@field}=#{CGI.escape(url)}")
             when :get then http.get("#{@action}?#{@field}=#{CGI.escape(url)}")
             end