My working Gists package.json & babelrc

.babelrc

{
    "presets": [
        "react",
        [
            "env",
            {
                "targets": {
                    "browsers": ["last 1 versions"]
                },
                "debug": true,
                "modules": "commonjs"
            }
        ]
    ],
    "plugins": [
        "transform-object-rest-spread",
        "transform-class-properties",
        "syntax-dynamic-import",
        "transform-runtime"
    ]
}

webpack.config.js

const path = require('path');
const ExtractTextPlugin = require("extract-text-webpack-plugin");
const HtmlWebpackPlugin = require('html-webpack-plugin');
const CleanWebpackPlugin = require('clean-webpack-plugin');
const CopyWebpackPlugin = require('copy-webpack-plugin');
const autoprefixer = require('autoprefixer');
const webpack = require('webpack');
const extractSass = new ExtractTextPlugin({
  filename: "[name].css",
  allChunks: false,
  disable: true
});

module.exports = {
  target: 'web',
  devtool: 'inline-source-map',
  entry: {
    'index': './src/index.js'
  },
  resolve: {
    alias: {
      commonfonts: path.resolve(__dirname, 'src/components/common/assets/fonts')
    }
  },
  output: {
    filename: '[name].bundle.js',
    chunkFilename: '[name].bundle.js',
    path: __dirname + '/build',
    publicPath: '/',
    sourceMapFilename: '[name].map',
    pathinfo: true,
  },
  module: {
    rules: [
      {
        test: /\.js$/,
        loader: [
          'babel-loader'
        ],
        exclude: [/node_modules/]
      },
      {
        test: /\.(scss|css)$/,
        use: extractSass.extract({
          use: [
            {
              loader: "css-loader",
              options: {
                sourceMap: true
              }
            },
            {
              loader: "sass-loader",
              options: {
                sourceMap: true
              }
            },
            {
              loader: require.resolve('postcss-loader'),
              options: {
                ident: 'postcss',
                plugins: () => [
                  autoprefixer({
                    browsers: [
                      '>1%',
                      'last 2 versions',
                      'Firefox ESR',
                      'not ie < 9', 
                    ],
                    flexbox: 'no-2009',
                  }),
                ],
              },
            },
          ],
          fallback: "style-loader" 
        })
      },
      {
        test: /\.(png|svg|jpe?g|gif)$/,
        use: [
          {
            loader: 'file-loader',
            options: {
              name: '[name].[ext]',
              outputPath: 'images/'
            }
          }
        ]
      },
      {
        test: /\.(woff|woff2|eot|ttf|otf)$/,
        use: [
          {
            loader: 'file-loader',
            options: {
              name: '[name].[ext]',
              outputPath: 'fonts/'
            }
          }
        ]
      }
    ]
  },
  plugins: [
    new CleanWebpackPlugin(['build']),
    extractSass,
    new HtmlWebpackPlugin({ title: 'Instarem.com', 'template': __dirname + '/src/index.tmpl.html' }),
    new webpack.optimize.CommonsChunkPlugin({ name: 'commonChunk' }),
    new CopyWebpackPlugin(
      [
        {
          from: 'src/**/*.+(png|jpg)',
          to: 'images/[name].[ext]'
        }
      ]
    )
  ],

  devServer: {
    contentBase: './build',
    port: 9000,
    historyApiFallback: true,
    host: 'localhost'
  }
}