lib/euler.rb
def method_missing method, *args, &block
      if args.empty?
        @config.send(method)
      else
        @config.send("#{method}=", args.first)
      end
    end
def method_missing method, *args, &block
      if args.empty?
        @config.send(method)
      else
        @config.send("#{method}=", args.first)
      end
    end
Initialize an empty OpenStruct to hold configuration options
 To set a config option call the corresponding method with an argument.
 To retrieve a config option call the corresponding method without an argument.