message: use commonjs in umd build
diff: -import { rollup } from 'rollup';
  -import flow from 'rollup-plugin-flow';
  -import buble from 'rollup-plugin-buble';
  -import resolve from 'rollup-plugin-node-resolve';
  -import commonjs from 'rollup-plugin-commonjs';
  -import replace from 'rollup-plugin-replace';
  -import nodent from 'rollup-plugin-nodent';
  -import uglify from 'uglify-js';
  -import fs from 'fs';
  -import path from 'path';
  -import chalk from 'chalk';
  -import mkdirpNode from 'mkdirp';
  -import { promisify } from 'util';
  -import config from './config';
  -import { version } from '../package.json';
  +const { rollup } = require('rollup');
  +const flow = require('rollup-plugin-flow');
  +const buble = require('rollup-plugin-buble');
  +const resolve = require('rollup-plugin-node-resolve');
  +const commonjs = require('rollup-plugin-commonjs');
  +const replace = require('rollup-plugin-replace');
  +const nodent = require('rollup-plugin-nodent');
  +const uglify = require('uglify-js');
  +const fs = require('fs');
  +const path = require('path');
  +const chalk = require('chalk');
  +const mkdirpNode = require('mkdirp');
  +const { promisify } = require('util');
  +const config = require('./config');
  +const { version } = require('../package.json');
  const inputOptions = {
  input: 'src/index.js',
  