NEW YORK (Reuters) - Hip-hop artists Macklemore & Ryan Lewis, R&B singer Bruno Mars and pop star Rihanna received nominations on Thursday for artist of the year, the top category at the annual American Music Awards, along with Taylor Swift and Justin Timberlake. Rapper will.i.am and singer Kelly Clarkson announced the names of the nominees in five of the top categories on the ABC television network news show "Good Morning America. ...