factorail using reduce

[jelambrar96]

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[tianyizheng02]

Why overwrite the existing implementation? This is harder to read than what we already have, and it's in fact much slower:

> python -m timeit -n 1000 "value = 1" "for i in range(1001):" "    value *= i"
1000 loops, best of 5: 32 usec per loop
> python -m timeit -n 1000 -s "from functools import reduce; from operator import mul" "value = 1 if 1000 in {0, 1} else reduce(mul, range(1, 1001))"
1000 loops, best of 5: 289 usec per loop

I'm sorry, but I see no good reason to favor this implementation over the existing one.