What is the title of the post that is owned by csgillespie and has the highest popularity?
"csgillespie" is the DisplayName of user; highest popularity refers to Max(ViewCount)
SELECT T1.Title FROM posts AS T1 INNER JOIN users AS T2 ON T1.OwnerUserId = T2.Id WHERE T2.DisplayName = 'csgillespie' ORDER BY T1.ViewCount DESC LIMIT 1