Reduce for simplify PR

[back2dos]

Still need to implement reduce for #24. After unsuccessfully banging my head against the wall for a while I'm gravitating towards thinking that reduce should be the basis of everything (and forEach is merely a reduce that accumulates Noise), but it's rather involved and I need to let the idea sink in, because I want to get things right this time around. The issue is here is just a reminder.

[kevinresol]

Will it cause problems if the compiler is able to (if it ever will) check for pureness of the reducer? Or is it just about the internals? Because I prefer having separated forEach and reduce in the public API

[back2dos]

Oh, yeah. In the public API they should be separate things. My point is rather that implementing reduce over forEach is actually trickier than the other way around.