开发环境配置:
1.安装 nodejs
2.全局安装 gulp
npm install gulp -g(全局安装，gulp指令可用)
3.配置package.json
npm init
4.本地安装依赖
npm install --save-dev gulp webpack del jshint babel-core babel-loader babel-preset-env babel-preset-es2015 babel-plugin-transform-object-assign cross-env