CLJS-382: use set to track visited requires so contains? works properly
CLJS-382: use set to track visited requires so contains? works properly

Signed-off-by: Stuart Sierra <1d6e1cf70ec6f9ab28d3ea4b27a49a77654d370e@stuartsierra.com>

mstang/clojurescript,mstang/clojurescript,mstang/clojurescript