add state UZYSPullToRefreshStateCanFinish to fix trigger multiple times when pull quickly and action quickly

[ivoryxiong]

in sample project, when RefreshActionHandler is not insertRowAtTop but reloadTableViewData , which logic just like :

- (void)reloadTableViewData {
    __weak typeof(self) weakSelf = self;
    [[HttpManager sharedManager] Get:@"http://example.com/api/list"
                      successHandler:^(id data) {
                          [weakSelf.tableView reloadData];
                          [weakSelf.tableView stopRefreshAnimation];
                      }];
}

if we drag tableview quickly and the api response fast, then RefreshActionHandler may called multiple times, because tableView have no method/delegate tell us "reloadData" has finished, so stopRefreshAnimation can not be call appropriately！