def method_missing(method, * args)
      value = with_file(method, * args)
      logger.debug "#{self}.method_missing(#{method.inspect}, #{args.inspect}) => #{value.inspect}"
      value
    end
def method_missing(method, * args)
      value = with_file(method, * args)
      logger.debug "#{self}.method_missing(#{method.inspect}, #{args.inspect}) => #{value.inspect}"
      value
    end
Short-hand access to config file by its name.

 Example:

   RConfig.provider(:foo) => RConfig.with_file(:provider).foo
   RConfig.provider.foo   => RConfig.with_file(:provider).foo