fix(datepicker): fire ngChange on today/clear button press

Closes #1379

src/datepicker/datepicker.js

@@ -366,7 +366,10 @@ function ($compile, $parse, $document, $position, dateFilter, datepickerPopupCon
       ngModel.$parsers.unshift(parseDate);
 
       // Inner change
-      scope.dateSelection = function() {
+      scope.dateSelection = function(dt) {
+        if (angular.isDefined(dt)) {
+          scope.date = dt;
+        }
         ngModel.$setViewValue(scope.date);
         ngModel.$render();
 
@@ -442,13 +445,11 @@ function ($compile, $parse, $document, $position, dateFilter, datepickerPopupCon
         }
       });
 
-      var $setModelValue = $parse(attrs.ngModel).assign;
-
       scope.today = function() {
-        $setModelValue(originalScope, new Date());
+        scope.dateSelection(new Date());
       };
       scope.clear = function() {
-        $setModelValue(originalScope, null);
+        scope.dateSelection(null);
       };
 
       var $popup = $compile(popupEl)(scope);

src/datepicker/test/datepicker.spec.js

@@ -1195,6 +1195,36 @@ describe('datepicker directive', function () {
           expect(buttonBarElement.css('display')).toBe('none');
         });
       });
+
+      describe('`ng-change`', function() {
+        beforeEach(inject(function() {
+          $rootScope.changeHandler = jasmine.createSpy('changeHandler');
+          var wrapElement = $compile('<div><input ng-model="date" datepicker-popup ng-change="changeHandler()"><div>')($rootScope);
+          $rootScope.$digest();
+          assignElements(wrapElement);
+          assignButtonBar();
+        }));
+
+        it('should be called when `today` is clicked', function() {
+          buttons.eq(0).click();
+          expect($rootScope.changeHandler).toHaveBeenCalled();
+        });
+
+        it('should not be called when `weeks` is clicked', function() {
+          buttons.eq(1).click();
+          expect($rootScope.changeHandler).not.toHaveBeenCalled();
+        });
+
+        it('should be called when `clear` is clicked', function() {
+          buttons.eq(2).click();
+          expect($rootScope.changeHandler).toHaveBeenCalled();
+        });
+
+        it('should not be called when `close` is clicked', function() {
+          buttons.eq(3).click();
+          expect($rootScope.changeHandler).not.toHaveBeenCalled();
+        });
+      });
     });
 
     describe('use with `ng-required` directive', function() {