Fix up really stupid thunking of reduce

apply_op just clamped functools.reduce to a single-arity form.  Dumb,
dumb, dumb (and pointless).  Let's just assign functools.reduce to
apply_op.
Don't assign to local namespace with partial

Let's make this blatant plagarism of reduce even less stupid.  Take out
the rediculous assignment altogether, and just:
from functools import reduce

There.