fix(ngTransclude): clear the translusion point before transcluding

when the transluded content is being teleported to the translusion point, we should ensure that
the translusion point is empty before appending otherwise we end up with junk before the transcluded
content

test/ng/compileSpec.js

@@ -2450,7 +2450,7 @@ describe('$compile', function() {
         element = $compile('<div parent-directive><div child-directive></div>childContentText;</div>')($rootScope);
         $rootScope.$apply();
         expect(log).toEqual('parentController; childController');
-        expect(element.text()).toBe('parentTemplateText;childTemplateText;childContentText;')
+        expect(element.text()).toBe('childTemplateText;childContentText;')
       });
     });
 
@@ -2554,7 +2554,7 @@ describe('$compile', function() {
                             '</div>')($rootScope);
         $rootScope.$apply();
         expect(log).toEqual('parentController; childController; babyController');
-        expect(element.text()).toBe('parentTemplateText;childTemplateText;childContentText;babyTemplateText;')
+        expect(element.text()).toBe('childContentText;babyTemplateText;')
       });
     });
 
@@ -2825,6 +2825,24 @@ describe('$compile', function() {
     });
 
 
+    it('should clear contents of the ng-translude element before appending transcluded content',
+        function() {
+      module(function() {
+        directive('trans', function() {
+          return {
+            transclude: true,
+            template: '<div ng-transclude>old stuff! </div>'
+          };
+        });
+      });
+      inject(function(log, $rootScope, $compile) {
+        element = $compile('<div trans>unicorn!</div>')($rootScope);
+        $rootScope.$apply();
+        expect(sortedHtml(element.html())).toEqual('<div ng-transclude=""><span>unicorn!</span></div>');
+      });
+    });
+
+
     it('should make the result of a transclusion available to the parent directive in post-linking phase (template)',
         function() {
       module(function() {