Check out the premiere of Rihanna’s latest video, “Man Down“! “ManDownVideo #brrrraaaaappp rah rah rah MO FYAH!!!! #RihannaNavy” the 23-year-old Bajan singer tweeted when the clip premiered online. FYI: Rapper B.o.B will be joining Rihanna on her North American Loud Tour! He was recently added as a special guest for nine concerts (other guests include Cee Lo Green and J….