title: Vue.js v-if inside v-for not actively listening to array change
body: <p>I am trying do display an element for each array inside an array and display that element if its array contains a true boolean. The if function runs the first time but the element does not disappear when the value changes.</p>
  
  <pre><code>&lt;li v-for="(value, index) in list"&gt;
      &lt;span&gt; {{ value[0] }} &lt;/span&gt;
      &lt;span v-if='value[1]'&gt; {{ value[2] }} &lt;/span&gt;
  &lt;/li&gt;
  
  
  var List = new Vue({
      el: "#List",
      data: {
          list: ['fizz',true,0],
  
      },
      methods: {
          toggleItem: function(index) {
              this.list[index][1] = !this.list[index][1];
          },
  
      }
  })
  </code></pre>
  
  <p>I should be able to run</p>
  
  <pre><code>List.toggleItem(0)
  </code></pre>