def run(args = ARGV)
      @args = args
      validate!
      Spanx::CLI.subclass_class(args.shift).new.run(args)
    end
def run(args = ARGV)
      @args = args
      validate!
      Spanx::CLI.subclass_class(args.shift).new.run(args)
    end
the first element of ARGV should be a subcommand, which maps to
 a class in spanx/cli/