expose beginUpdates and endUpdates

AsyncDisplayKit/ASCollectionNode.mm

@@ -187,6 +187,16 @@
   [self.view clearFetchedData];
 }
 
+- (void)beginUpdates
+{
+    [self.view.dataController beginUpdates];
+}
+
+- (void)endUpdatesAnimated:(BOOL)animated
+{
+    [self.view.dataController endUpdatesAnimated:animated completion:nil];
+}
+
 #pragma mark - ASCollectionView Forwards
 
 - (ASRangeTuningParameters)tuningParametersForRangeType:(ASLayoutRangeType)rangeType