On this edition of Conversations, Elizabeth Marshall Thomas talks with host Dan Skinner about “Growing Old: Notes on Aging With Something Like Grace.” Thomas has written 16 books during her half-century-long career. Her fifth book, “The Hidden Life of Dogs,” spent a year on the New York Times bestseller list, and her book on cats, “Tribe of Tiger,” was an international bestseller. At age 88, she decided it was time to write about getting old.