Commit peekAheadIter

Creates an iterator out of iterable and yields tuples of form: (item,
next item)
the final iteration will yield (last item, None)
Example:
>>>for i in peekAheadIter(range(5)): print i
(0, 1)
(1, 2)
(2, 3)
(3, 4)
(4, None)