Photo by Jesse Kimes There’s a difference between nostalgia and timelessness, and Illinois rappers The Cool Kids walk on a tightrope very gingerly between the two. Everything from their wardrobe choice (a Penny Hardaway jersey and a Police T-shirt) to their lyrics (“I’m the only third grader in this school with a beeper,”) suggest a hefty nostalgia for the late 1980s and early ’90s. They’ve even referred to themselves as the “Black Beastie Boys”…