Remove one-line method.
Refactoring from ClojureHNL #002 meetup.

* Demonstrate for comprehensions and destructuring.
* Remove unnecessary storage of new-x/y, allow "accumulation" of
  position information to be stored in the noise function.
* Use separate map+draw and reduce+update+reset steps to replace
  for comprehension and update function which contained a drawing
  side-effect.