title: Vue not working in a simple example
body: <p>Here is my code and i seem to have done everything correctly.
  what might be the problem as the output is only {{message}}</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html lang="en"&gt;
  &lt;head&gt;
      &lt;meta charset="UTF-8"&gt;
      &lt;title&gt;Title&lt;/title&gt;
  
  &lt;/head&gt;
  &lt;body&gt;
  &lt;div id="app"&gt;
  &lt;h1&gt;{{message}}&lt;/h1&gt;
  &lt;/div&gt;
  
  &lt;script src="https://vuejs.org/js/vue.js"/&gt;
  &lt;script&gt;
      new Vue({
          el: '#app',
          data:{
              message: "Yow"
          },
          mounted: function () {
              console.log("Mounted")
          }
      });
  &lt;/script&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>and it just outputs {{message}}</p>