fix tests for browsers that do not support Map, Set, WeakMap or WeakSet
fix tests for browsers that do not support Map, Set, WeakMap or WeakSet

jdelbello/underscore,rlugojr/underscore,keepgoingwm/underscore,keepgoingwm/underscore,jashkenas/underscore,akre54/underscore,documentcloud/underscore,tnga/underscore-es,documentcloud/underscore,jdelbello/underscore,tnga/underscore-es,jashkenas/underscore,rlugojr/underscore,akre54/underscore,jpalomar/underscore,jpalomar/underscore