code: function flow (functions) {
    if (!functions.length) {
      return function (arg) { return arg }
    }
  
    return function () {
      var result = functions[0].apply(this, arguments)
      for (var i = 1; i < functions.length; i++) {
        result = functions[i](result)
      }
      return result
    }
  }
docs: Like `compose`, but left-to-right. flow([f, g])(x) = g(f(x))