def stack(options = {})
      @stack ||= begin
        builder_class = if defined?(Faraday::RackBuilder)
                          Faraday::RackBuilder
                        else
                          Faraday::Builder
                        end
        builder_class.new(&Github.default_middleware(options))
      end
    end
def stack(options = {})
      @stack ||= begin
        builder_class = if defined?(Faraday::RackBuilder)
                          Faraday::RackBuilder
                        else
                          Faraday::Builder
                        end
        builder_class.new(&Github.default_middleware(options))
      end
    end
Exposes middleware builder to facilitate custom stacks and easy
 addition of new extensions such as cache adapter.

 @api public