title: moment value can not init data-picker module
body: <p>I use <strong>$scope.dt= moment().format("YYYY-MM-DD")</strong> to init datapicker module.<br/>
  <code>&lt;p class="input-group"&gt;
          &lt;input type="text" class="form-control" uib-datepicker-popup ng-model="dt" is-open="popup2.opened" datepicker-options="dateOptions" ng-required="true" close-text="Close" /&gt;
          &lt;span class="input-group-btn"&gt;
              &lt;button type="button" class="btn btn-default" ng-click="open2()"&gt;
                &lt;i class="glyphicon glyphicon-calendar"&gt;&lt;/i&gt;
              &lt;/button&gt;
            &lt;/span&gt;
        &lt;/p&gt;</code></p>
  
  <p>this is plnkr <a href="http://embed.plnkr.co/fcXYx6/" rel="nofollow">test code.</a>.
  why this can not show value on input?</p>