title: Select All Feature in v-select not save all the items
body: <p>I am trying to add a select all button to the v-select component of vuetify. I am able to select all the options with the button but when I click on save it doesn't save all the items. But if I manually choose all the opens one by one and then click on save then all the items from the dropdown are saved. Please help me find the problem.</p>
  
  <pre><code>&lt;template&gt;
   &lt;v-select
    :items="documents"
    v-model="user.versions"
    :closeOnSelect="true"
    multiple
    attach
    auto
    item-text='name'
    item-value='id'&gt;
   &lt;/v-select&gt;
   &lt;v-btn class="red-button" @click='selectAll'&gt;Select&lt;/v-btn&gt;
   &lt;v-btn class="red-save-btn" @click='submitDocuments'&gt;&lt;i class="material-icons edit"&gt;save&lt;/i&gt; Save&lt;/v-btn&gt;
  &lt;/template&gt;
  
  &lt;script&gt;
   export default {
    props: ['user'],
    data: function () {
        return {
         documents: [],
         versions: []
        }
    },
    methods: {
     selectAll (){
      this.user.versions = [...this.documents]
      },
     submitDocuments() {
          var that = this;
          this.$axios.put(`/my_account/users/${this.user.id}.json`, {user: this.user})
     }
   }
  }
  &lt;/script&gt;
  </code></pre>