'One of the greatest CEOs ever': Jamie Dimon, Bill Gates and others on Warren Buffett's retirement

Warren Buffett said this weekend that he will retire as the head of Berkshire Hathaway (BRK.A) at the end of the year, ending a legendary investing career that saw him beat the market year after year and earned him the nickname “Oracle of Omaha.” Greg Abel, Buffett’s longtime heir apparent, will…