fix(datepicker): fix popup to work with ng-model-options:updateOn='default'

[B8li]

When using datepicker with popup and ng-model-options="{ updateOn: 'default'}", value can not be set via popup.

Plnkr with the problem(and hacky solution):
http://plnkr.co/edit/4LLbxCkWBzoPwJuOAbye?p=preview

This PR fixes this problem and selection(update model) via datepicker popup is possible again.

Use case for this scenario

Often we define ng-model-options={ updateOn: 'blur'} for multiple wrapped elements(e.g form).
For datepicker that is inside that element(form) usually doesn't make sense to update model value on blur, so we need to add ng-model-options to the datepicker element.

Technical information

AngularJS directive ng-model-options parses the given expression and object that is set to ngModel.$options is different then the object in expression. Here is ngModelOptions directives from angularJS code that changes this:

var ngModelOptionsDirective = function() {
  return {
    restrict: 'A',
    controller: ['$scope', '$attrs', function($scope, $attrs) {
      var that = this;
      this.$options = copy($scope.$eval($attrs.ngModelOptions));
      // Allow adding/overriding bound events
      if (isDefined(this.$options.updateOn)) {
        this.$options.updateOnDefault = false;
        // extract "default" pseudo-event from list of events that can trigger a model update
        this.$options.updateOn = trim(this.$options.updateOn.replace(DEFAULT_REGEXP, function() {
          that.$options.updateOnDefault = true;
          return ' ';
        }));
      } else {
        this.$options.updateOnDefault = true;
      }
    }]
  };

So when we use ngModelOptions.$options value to compile uib-datepicker-popup-wrap , we lose updateOn property and ngModel can not be updated using the pop up.

[wesleycho]

LGTM - thanks for this subtle catch...don't like how Angular seems to handle this.