center customTitleView fixed for xcode 8 builds

ios/RCCCustomTitleView.m

 
 - (void)rootViewDidChangeIntrinsicSize:(RCTRootView *)rootView {
     if ([self.alignment isEqualToString:@"center"]) {
-        [self setFrame:CGRectMake(0, 0, rootView.intrinsicContentSize.width, rootView.intrinsicContentSize.height)];
+        [self setFrame:CGRectMake(self.frame.origin.x, self.frame.origin.y, self.subView.intrinsicContentSize.width, self.subView.intrinsicContentSize.height)];
         [self.subView setFrame:CGRectMake(0, 0, rootView.intrinsicContentSize.width, rootView.intrinsicContentSize.height)];
     }
 }