title: how to clear checkbox checked status? with vue
body: <p>when i click next button, i want to remove checkbox checked status,
  but i don't use vue to remove it.
  this is demo code:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>new Vue({
    el: "#app",
    data: {
      id:0, 
      items: [
      {'id':1,'name':'chk-a','options':['a1','b1','c1','d1']},
      {'id':2,'name':'chk-b','options':['a2','b2','c2','d2']},
      {'id':3,'name':'chk-c','options':['a3','b3','c3','d3']},
      {'id':4,'name':'chk-d','options':['a4','b4','c4','d4']},
      ]
    },
    methods: {
      next: function (id) {
        if(id&lt;this.items.length){
          this.id++ 
        }
      }
    }
  });</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;script src="https://cdnjs.cloudflare.com/ajax/libs/vue/2.5.3/vue.min.js"&gt;&lt;/script&gt;
  &lt;div id="app"&gt;
    &lt;h1&gt;Checkbox&lt;/h1&gt;
    &lt;div v-for="item in items[id].options"&gt;
      &lt;input type="radio" name="chk" :id="id"&gt;
      &lt;label for="two"&gt;{{item}}&lt;/label&gt;
    &lt;/div&gt;
    &lt;button @click="next(id+1)"&gt;Next&lt;/button&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>