title: webpack-dev-server serves one-version-old bundle
body: <p>I am using Webpack to build an Angular 2 AOT app (see config below). When I just run <code>webpack</code> everything works fine. When I use <code>webpack-dev-server</code>, it works fine for the first page load, but from then on the bundle is always one version old.</p>
  
  <p>For example, when I start up the server with an Angular component template containing <code>&lt;h1&gt;hello&lt;/h1&gt;</code> I see "hello" as expected. When I then change the template to <code>&lt;h1&gt;hello world&lt;/h1&gt;</code>, the page reloads but still only reads "hello" (and the console says <code>[WDS] Nothing changed.</code>) When I then change the template <em>again</em> to <code>&lt;h1&gt;goodbye world&lt;/h1&gt;</code>, the page reloads but reads "hello world" as it should have on the previous reload.</p>
  
  <p>This delay does not happen with <code>index.html</code> (even though I am using <code>html-webpack-plugin</code>), only with TypeScript files and Angular templates (which are compiled to TypeScript files). It also does not happen with <code>webpack --watch</code>, only with <code>webpack-dev-server</code>.</p>
  
  <p>My <code>webpack.config.js</code>:</p>
  
  <pre><code>const webpack = require("webpack");
  const ngToolsWebpack = require("@ngtools/webpack");
  const HtmlWebpackPlugin = require("html-webpack-plugin");
  
  module.exports = {
      entry: {
          app: "./src/main.ts",
          vendor: ["@angular/core", "@angular/common", "@angular/platform-browser"],
          polyfill: ["zone.js/dist/zone.js"],
      },
      output: {
          path: __dirname + "/dist",
          filename: "[name].js",
      },
  
      resolve: {
          extensions: [".ts", ".js"],
      },
  
      module: {
          rules: [
              { test: /\.html$/, use: "raw-loader" },
              { test: /\.css$/, use: "raw-loader" },
              { test: /\.ts$/, use: "@ngtools/webpack" },
          ],
      },
  
      plugins: [
          new ngToolsWebpack.AotPlugin({
              tsConfigPath: "./tsconfig.json",
          }),
          new webpack.optimize.CommonsChunkPlugin({
              names: ["vendor", "polyfill"],
          }),
          new HtmlWebpackPlugin({
              template: "src/index.html",
          }),
      ],
  };
  </code></pre>