A century of Jimmy Carter: Longest-living former president turns 100

USA TODAY - For more and to sign up click here Judy Kurtz In 1998, at the ripe age of 74, former President Jimmy Carter put some of his thoughts about getting older to paper. "The virtues of aging," Carter wrote in a book that year, "include both the blessings that come to us as we grow older and what we have to offer that might be beneficial to others." It turns out that Carter, who hit 100 on Tuesday, still had…