title: Webpack fails to mount Vue components
body: <p>After using Webpack with Vue to compile a project, when I open a page that uses a Vue component I get:</p>
  
  <blockquote>
    <p><code>[Vue warn]: Failed to mount component: template or render function not defined.</code></p>
  </blockquote>
  
  <p>and in place of the component Vue renders</p>
  
  <pre><code>&lt;-- function (a, b, c, d) { return createElement(vm, a, b, c, d, true); } --&gt;
  </code></pre>
  
  <p>Why does this error happen?</p>
  
  <p>Note: <a href="https://gist.github.com/RedHatter/8eadc65bd5f8327f26dcfd10a7bf3dad" rel="nofollow noreferrer">I've created an MCVE for this problem.</a> The exact Webpack config used is:</p>
  
  <pre><code>module.exports = {
    entry: __dirname + '/display.js',
    output: {
      filename: 'bundle.js'
    },
    module: {
      rules: [ { test: /\.vue$/, loader: 'vue-loader' } ]
    }
  }
  </code></pre>