title: Isn't webpack dev server generating bundle.js in memory?
body: <p>I have a file structure as below:</p>
  
  <pre><code>Project
   |
   +-- src/
   |   |
   |   +-- index.js
   |
   +-- index.html
   |
   +-- webpack.config.js
  </code></pre>
  
  <p>src/index.js:</p>
  
  <pre><code>document.write("Hello World.");
  </code></pre>
  
  <p>index.html:</p>
  
  <pre><code> &lt;!DOCTYPE html&gt;
  &lt;html lang="en"&gt;
  &lt;head&gt;
      &lt;meta charset="UTF-8"&gt;
      &lt;title&gt;webpack learning&lt;/title&gt;
  
      &lt;script src="builds/bundle.js"&gt;&lt;/script&gt;
  &lt;/head&gt;
  &lt;body&gt;
  
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>webpack.config.js:</p>
  
  <pre><code>var path = require('path');
  
  module.exports = {
    entry: './src',
    output: {
      path: path.join(__dirname, 'builds'),
      filename: 'bundle.js',
    }
  };
  </code></pre>
  
  <p>When I run webpack-dev-server in the Project directory, webpack-dev-server starts normally and prints "webpack: bundle is now VALID." However, when I launch a browser and go to localhost:8080, the console complains that bundle.js is not found. Indeed, there is no such folder named "build" with bundle.js in it. But, isn't webpack-dev-server generating bundle.js in memory? Any configuration problems involved?</p>