The claymation animator Adam Elliot doesn’t want his films to look too perfect. He celebrates the bumps and cracks in the clay, just as he celebrates the flaws in his characters. The World’s Sarah Birnbaum talks to Elliot about his newest film, “Memoir of a Snail,” which touches on themes of bullying, hoarding, alcoholism, loneliness and grief… with a big dose of gallows humor.