title: Angular Material Contact Chips validation ng-minlength/maxlength/required
body: <p>I've been trying to trigger a validation error on <code>&lt;md-contact-chips&gt;</code> for ng-minlength/maxlength/required but haven't been able to implement this effectively. </p>
  
  <p>Is there a straight forward way to implement this myself? -- it seems for some reason that the contact chips directive in Angular Material does not support these validations.</p>
  
  <p>See codepen here:
  <a href="http://codepen.io/anon/pen/YqdRNw" rel="nofollow">http://codepen.io/anon/pen/YqdRNw</a></p>
  
  <pre><code>&lt;form name='myForm'&gt;
  &lt;div ng-controller="ContactChipDemoCtrl as ctrl" layout="column" ng-cloak="" class="chipsdemoContactChips" ng-app="MyApp"&gt;
    &lt;md-content class="md-padding autocomplete" layout="column"&gt;
      &lt;md-contact-chips ng-model="ctrl.contacts" ng-minlength='1' ng-required='true' ng-maxlenght='3' name='contacts' md-contacts="ctrl.querySearch($query)" md-contact-name="name" md-contact-image="image" md-contact-email="email" md-require-match="true" md-highlight-flags="i" filter-selected="ctrl.filterSelected" placeholder="To" &gt;
      &lt;/md-contact-chips&gt;
      &lt;p ng-show="myForm.contacts.$error.required" class="text-danger"&gt;You did not enter a contact&lt;/p&gt;
      &lt;p ng-show="myForm.contacts.$error.minlength" class="text-danger"&gt;Your contact list is too short&lt;/p&gt;
      &lt;p ng-show="myForm.contacts.$error.maxlength" class="text-danger"&gt;Your contact list is too long&lt;/p&gt;
    &lt;/md-content&gt;
  &lt;/div&gt;
  &lt;/form&gt;
  </code></pre>