instanceof fails when the constructor object is from a different iframe than the obj was created with. Also, the undefined check isn't helpful.
Adding arguments support to isEmpty.
Merge pull request #4 from ljharb/is_empty_arguments

Adding arguments support to isEmpty
Merge pull request #5 from ljharb/fix_instance_of

Fix instance of
Updated is-extended.min.js fixed window.alter isFunction in <ie9 and few more tests