Please name the coin that ranked first among the coins traded on April 29, 2013.
ranked first refers to cmc_rank = 1; on April 29, 2013 refers to date = '2013-04-29'
SELECT T1.name FROM coins AS T1 INNER JOIN historical AS T2 ON T1.id = T2.coin_id WHERE T2.date = '2013-04-29' AND T2.cmc_rank = 1