(SYRefreshTable)IOS下拉刷新，上拉加载更多组件

Pull to Refresh

*  - (BOOL)refresh
   {
      if (![super refresh])
         return NO;

      self.pageCount = 1;

      [lockLoadData lock];
      [self performSelector:@selector(loadItemData) withObject:nil afterDelay:0.01];
      [lockLoadData unlock];

      return YES;
   }

Load More

*  - (BOOL)loadMore
   {
       if (![super loadMore])
          return NO;

       self.pageCount ++;

       [lockLoadData lock];
       [self performSelector:@selector(loadItemData) withObject:nil afterDelay:0.01];
       [lockLoadData unlock];

       return YES;
   }

UIScrollViewDelegate Method

*  - (void)scrollViewDidScroll:(UIScrollView *)scrollView
   {
      [super scrollViewDidScroll:scrollView];
   }