(Releads on Madison) * Britain top medals with five gold * Set for strong Olympic challenge in Rio By Martyn Herman LONDON, March 6 (Reuters) - Bradley Wiggins and Mark Cavendish provided a rip-roaring climax to the world track cycling championships with a stunning Madison victory that rocked London's velodrome to its rafters on Sunday. The two British cycling greats, who fell out when they failed to claim an Olympic medal in the 200-lap event at the 2008 Beijing Games, came from nowhere to carve their way to victory and give the hosts a table-topping fifth gold medal. Five months before the start of the Rio Olympics, Britain again look like the team to beat after failing to win any golds at last year's world championships. More...