Trailers Weekly: “The Secret Life Of Walter Mitty”, “American Hustle”, “Jackass Presents: Bad Grandpa”, “Machete Kills”, “Riddick” Michael Lee, August 3, 2013 Trailers Weekly is a feature in which we bring you the most popular and talked about trailers of the week. Sharing trailers is a classic viral practice, and trailers are still the most mainstream way for people to learn about movies. We’ve got trailers from The Secret Life of Walter…