title: VueJS Datepicker wil not accept dd/MM/yy
body: <p>UPDATE:</p>
  
  <p>This is a bug and I have raised it as an issue on github.  TBH, the component is not really ready for mainstream use yet.</p>
  
  <hr>
  
  <p>My <code>vuejs-datepicker</code> will not accept a dd/mm/yy format if the day is 13 or greater.  Presumably this is because it is interpreting the first two digits to be the month, and therefore rejects anything greater than 12.</p>
  
  <p>The calendar pops up.  You can select a date, and it shows in the input field.  However, as soon as the field loses focus, it is cleared.</p>
  
  <p>I have tried using both a static string as the value of <code>format</code>, and a function.  Below is the function version.</p>
  
  <p>HTML:</p>
  
  <pre><code>&lt;div id="respond_by"&gt;
      &lt;date-picker name="respond_by"&gt;&lt;/date-picker&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Script at foot of page:</p>
  
  <pre><code>&lt;script&gt;
      $(function () {
          new Vue({ el: "#respond_by" });
      });
  &lt;/script&gt;
  </code></pre>
  
  <p>My single file component:</p>
  
  <pre><code>&lt;template&gt;
      &lt;vue-date-picker placeholder="dd/mm/yy"
                       input-class="form-control"
                       :name="name"
                       :format="customDateFormat"
                       monday-first
                       typeable&gt;&lt;/vue-date-picker&gt;
  &lt;/template&gt;
  
  &lt;script&gt;
      import moment from 'moment';
      import DatePicker from 'vuejs-datepicker';
  
      export default {
          props : [
              'name'
          ],
          components: {
              'vue-date-picker' : DatePicker
          },
          methods: {
              customDateFormat(date) {
                  return moment(date).format('DD/MM/YY');
              }
          }
      }
  &lt;/script&gt;
  </code></pre>
  
  <p>Globally registering the component:</p>
  
  <pre><code>import DatePicker from './date-time/date-picker.vue';
  Vue.component('date-picker', DatePicker);
  </code></pre>
  
  <p>I have tested both Firefox and Chrome, with the same result.</p>
  
  <p>I have tested the <code>vuejs-datepicker</code> code sand box and it works fine there, <a href="https://codesandbox.io/s/mpklq49wp" rel="nofollow noreferrer">https://codesandbox.io/s/mpklq49wp</a>.  I tested it by adding the following line to the list of options in the formatting example:</p>
  
  <pre><code>&lt;option value="dd/MM/yy"&gt;dd/MM/yy - e.g 13/11/18&lt;/option&gt;
  </code></pre>