How to write config block for gems. Inspired by http://rarlindseysmash.com/posts/config-and-generators-in-gems

gem_config.rb

module Jem
  class << self
    attr_accessor :configuration
  end

  def self.configure
    self.configuration ||= Configuration.new
    yield(configuration)
  end

  class Configuration
    attr_accessor :option

    def initialize
      @option = 'default_option'
    end
  end
end