.babelrc

{
    "presets": [
        ["stage-0"],
        ["env", {"modules": false}],
        "react"
    ],
    "plugins": [
        "react-hot-loader/babel"
        //"react-css-modules"
    ]
}

postcss.config.js

module.exports = {
    plugins: [
        require ('autoprefixer')
    ]
}

webpack.config.js

const path = require('path');
const webpack = require('webpack');
const env = require ('node-env-file');
const HtmlWebpackPlugin = require('html-webpack-plugin');
const ExtractTextPlugin = require("extract-text-webpack-plugin");

env (path.join(__dirname, ".env"));

const isProd = process.env.NODE_ENV === 'prod';

const prodCss = ExtractTextPlugin.extract({
    fallback: 'style-loader',
    use: [{
        loader: 'css-loader',
        options: {
            modules: true,
            localIdentName: '[path][name]__[local]--[hash:base64:5]'
        }}, 'postcss-loader', 
        'sass-loader'
    ],
    publicPath: '/dist'
});
const devCss =  [
    'style-loader', {
        loader: 'css-loader',
        options: {
            modules: true,
            localIdentName: '[path][name]__[local]--[hash:base64:5]'
        }
    }, 
    'postcss-loader',
    'sass-loader'
];

const css = isProd? prodCss : devCss;
const id = isProd? '[hash]' : 'bundle';

module.exports = {
    entry: [
        'react-hot-loader/patch',
        'webpack-dev-server/client?http://localhost:8080',
        'webpack/hot/only-dev-server',
        './src/app.js',
    ],
    output: {
        path: path.join (__dirname, 'dist'),
        filename: '[name].' + id + '.js',
        chunkFilename: '[id].' + id + '.js'
    },
    module: {
        rules: [{
            test: /\.(sa|s?c)ss$/,
            use: css
        }, {
            test: /\.jsx?$/,
            exclude: /node_modules/,
            use: 'babel-loader'
        }]
    },
    plugins: [
        new HtmlWebpackPlugin ({
            title: 'Webpack test page',
            template: 'src/index.html',
            cache: true
        }),
        new ExtractTextPlugin({
            filename: '[name].' + id + '.css',
            disable: !isProd,
            allChunks: true
        }),
        new webpack.HotModuleReplacementPlugin(),
        new webpack.NamedModulesPlugin(),
        new webpack.optimize.CommonsChunkPlugin({
            name: 'vendor',
            minChunks: function (module) {
                return module.context && module.context.indexOf('node_modules') !== -1;
            }
        })
    ],
    devServer: {
        compress: true,
        contentBase: path.join (__dirname, 'assets'),
        overlay: true,
        hot: !isProd,
        proxy: {
            '/api': {
                target: 'http://localhost:3000/',
                secure: false
            }
        }
    }
};