webpack配置文件拆分

1、拆开base和各环境的配置，通过merge进行合并
2、热更新，起来老是白屏，加了个插件，把路径重新写了一下

entry: './src/main.js',
    output: {
        path: path.resolve(__dirname, 'dist'),
        publicPath: '/',
        filename: 'build.js'
    },
plugins: [
        new webpack.HotModuleReplacementPlugin()
    ],
// package.json
webpack-dev-server  --hot  --inline --progress --config build/webpack.dev.config.js