控制一个cell不可被移动到另外一个section中

- (NSIndexPath *) tableView:(UITableView *)tableView targetIndexPathForMoveFromRowAtIndexPath:(NSIndexPath *)sourceIndexPath toProposedIndexPath:(NSIndexPath *)proposedDestinationIndexPath {

return sourceIndexPath.section == proposedDestinationIndexPath.section ? proposedDestinationIndexPath : sourceIndexPath;

}