ENH: make Series work with map objects the same way as generators

ideally also create a class that is a sub-class of ``collections.Iterable`` (you need to define ``__getitem__/__len__`` IIRC). to test this as well. (e.g. look for how to do this in ``tests_frames/test_constructor_sequence_like``).

Further I don't think ``Generator`` is actually tested explicity. can you add one for that?

thxs