title: How to set datepicker minDate?
body: <p>I have a directive date-picker.js and view as selectDate.html. I want to set minDate for the date picker when the value of another datepicker changes. How to achieve that?</p>
  
  <pre><code>.directive('selectDate', ['moment', function(moment) {
      return {
          restrict: 'E',
          require:'^ngModel',
          templateUrl: 'views/selectDate.html',
          replace: true,
          scope: {
              ngModel: '='
          },
          link: function($scope, element, attrs) {
              $scope.date = $scope.ngModel;
              $scope.dateOptions = {
                  startingDay: 1,
                  showWeeks: false
              };
              $scope.dateStatus = {
                  opened: false
              };
              $scope.openDatePopup = function() {
                  $scope.dateStatus.opened = true;
              };
              $scope.$watch('date', function (newValue, oldValue) {
                  if (newValue !== oldValue) {
                      var date = moment(newValue);
                      $scope.ngModel = date.format('YYYY-MM-DD');
                  }
              });
          }
      };
  </code></pre>
  
  <p><strong>selectDate.html</strong></p>
  
  <pre><code>&lt;span class="select-date"&gt;
    &lt;input type="text" readonly="readonly" datepicker-popup="dd.MM.yyyy"     datepicker-options="{startingDay: 1, showWeeks: true}" ng-model="date"   show-button-bar="false" current-text="Heute" close-text="Schließen" is-  open="dateStatus.opened" min-date="'2014-01-01'" class="form-control" required="required" ng-click="openDatePopup()"&gt;
  &lt;/span&gt;
  </code></pre>
  
  <p>I am using it like below:</p>
  
  <pre><code>   From &lt;select-date ng-model="fromDate"&gt;&lt;/select-date&gt;
     To &lt;select-date ng-model="toDate"&gt;&lt;/select-date&gt;
  </code></pre>
  
  <p>I want to set minDate of toDate to fromDate value. </p>