Add a cycle built-in based on itertools.cycle

[evhub]

Approximate implementation:

def cycle(iterable, times=None):
    iterable = reiterable(iterable)
    i = 0
    while times is None or i < times:
        yield from iterable
        i += 1

Should also support enhanced built-in methods (e.g. __len__, count, etc.). Should have numpy support for finite times.