Julie Klausner plays an unsuccessful comic who quips about celebrities in her Hulu series, 'Difficult People.' She says that she and her co-star Billy Eichner bonded over their shared love of show business and pop culture. John Powers reviews ‘War Dogs,’ a new comedy about the business of war. Science writer Ed Yong says billions of microbes that live on and within our bodies affect digestion, immunity, body weight and general health. His new book is 'I Contain Multitudes.'