更新tabBarItem的图片

fristNav.tabBarItem.image = [[UIImage imageNamed:@"index_tab_010.png"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];
fristNav.tabBarItem.selectedImage = [[UIImage imageNamed:@"index_tab_011.png"] imageWithRenderingMode:UIImageRenderingModeAlwaysOriginal];