title: React router can't find page after page refresh
body: <p>My App is displaying a list of books with links to a detail page about the book.</p>
  
  <p>When I am on the home component where the book list is rendered and click on a link to get to a specific book, the page is loading correctly...</p>
  
  <p>But when I refresh the page, there is a 404 - Page not found error</p>
  
  <p>(I'm using react-router v4, Node v6.11.1, Express v4.15.2)</p>
  
  <p><strong>React Router setup:</strong></p>
  
  <pre><code>import { BrowserRouter as Router  } from 'react-router-dom'
  import { Switch, Route } from 'react-router-dom'
  
  class App extends Component {
      render() {
          return (
              &lt;div&gt;
                  &lt;MyNavbar/&gt;
                  &lt;div style={{paddingTop: "5rem"}}&gt;
                      &lt;Switch&gt;
                          &lt;Route exact path='/' component={Home}/&gt;
                          &lt;Route path='/book/:id' component={BookPage}/&gt;
                      &lt;/Switch&gt;
                  &lt;/div&gt;
              &lt;/div&gt;
          )
      }
  }
  
  ReactDOM.render((
      &lt;Router&gt;
          &lt;App /&gt;
      &lt;/Router&gt;
  ), document.getElementById('root'))
  </code></pre>
  
  <p><strong>This is my webpack config:</strong></p>
  
  <pre><code>var webpack = require('webpack')
  var path = require('path')
  
  module.exports = {
      entry: {
          app: './src/app.js'
      },
      output: {
          filename: 'public/dist/bundle.js',
          sourceMapFilename: 'public/dist/bundle.map.js'
      },
      devtool: '#source-map',
      module: {
          loaders: [
              {
                  loader: 'babel-loader',
                  test: /\.js?$/,
                  exclude: /(node_modules)/,
                  query: {
                      presets: ['react', 'es2015']
                  }
              }, {
                  test: /\.css$/,
                  loader: "style-loader!css-loader"
              },
              {
                  test: /\.scss$/,
                  use: [
                      'style-loader',
                      'css-loader',
                      { loader: 'sass-loader', options: { sourceMap: true } }
                  ]
              },
              {
                  test: /\.(png|jpg|)$/,
                  loader: 'url-loader?limit=200000&amp;name=./imgs/[hash].[ext]'
              }
          ]
      },
  }
  </code></pre>