How many coins were added in May 2013? Please list the names of coins.
in May 2013 refers to year(date_added) = 2013 and month(date_added) = 5
SELECT COUNT(id) num FROM coins WHERE STRFTIME('%Y-%m', date_added) = '2013-05' UNION ALL SELECT name FROM coins WHERE STRFTIME('%Y-%m', date_added) = '2013-05'