When was the last time you saw a live performing circus? Chances are you’ve simply forgotten about circus as a type of performing arts. Indeed, with so many blockbuster movies filled with otherworldly acrobatics, there seems to be a loss of interest in seeing an actual human being putting their life at risk for your entertainment. Nevertheless, the entertaining teams of performers — from Cirque du Soleil to The Big Apple Circus — still deliver some of the most gut-wrenching and captivating shows to people across the world. Last week, Boston hosted the world’s renowned Australian ensemble of acrobats, musicians, and dancers known as Circus Oz.