webpack vue-loader

相比vue-loader V14, V15配置上有重大变化，需要在webpack.config.js中声明以下内容
参考vue-loader官方文档

// webpack.config.js
//Vue Loader v15 now requires an accompanying webpack plugin to function properly
const VueLoaderPlugin = require('vue-loader/lib/plugin')

module.exports = {
  // ...
  plugins: [
    new VueLoaderPlugin()
  ]
}