simplify callback signature, close #38, close #39
simplify callback signature, close #38, close #39

timkuijsten/levelup,toddself/levelup,JTKnox91/levelup,timkuijsten/levelup,djchie/levelup,roppa/levelup,Level/levelup,lastguest/levelup,djchie/levelup,lastguest/levelup,toddself/levelup,JTKnox91/levelup,roppa/levelup