Crunch Gym is squeezing its personal trainers — paying the fitness instructors just $8.75 an hour for one-on-one sessions and refusing to compensate them at all for other duties like meetings and cleaning, according to a new class-action lawsuit. Arielle Jernigan, who worked at the East 59th Street location from 2015 to 2016, and Kadeem Johnson, who is still employed there, filed the suit in…