Nwise itertools

Thanks for this. This is much nicer recipe than the current one IMO. Unfortunately, wasn’t able to extend it for n_partials parameter. At least not yet.

Apologies for mixing in another thread, but I think Itertools.ilen(iterable) is part of the same book. I am curious what is your opinion on ilen addition to itertools (from the perspective of more_itertools maintainer)?