title: Vuejs v-model not updating
body: <p>My "hello" data property is not updating whenever I update the value in the text field. The value in {{hello}} should change as I modify the value in the text field. Here is a video that demonstrates what I'm trying to do: <a href="https://www.youtube.com/watch?v=9rmfaA-ndak" rel="nofollow noreferrer">https://www.youtube.com/watch?v=9rmfaA-ndak</a></p>
  
  <pre><code>&lt;div id="app"&gt;
    &lt;example&gt;&lt;/example&gt;
  &lt;/div&gt;
  
  &lt;template id="template"&gt;
    &lt;input type="text" placeholder="target env" id="field_target_env" :v-model="hello"&gt;{{ hello }}
  &lt;/template&gt;
  </code></pre>
  
  <pre><code>Vue.component('example', {
    template: '#template',
    data() {
      return {
          hello: '242'
      }
    }
  });
  
  var vm = new Vue({
    el: '#app'
  });
  </code></pre>
  
  <p>Here is runnable
  jsfiddle: <a href="https://jsfiddle.net/3akv5e4f/4/" rel="nofollow noreferrer">https://jsfiddle.net/3akv5e4f/4/</a></p>