Implement Logging driver for debugging side-effects

[xtianjohns]

There are instances where side-effecting output is located inside a component's main function, instead of in a driver.

I suggest implementing a driver to wire up these kinds of effects. Example usage, relative to linked 'leaked' effects:

export default function Scratchpad (DOM, props) {
  // ...
  const error$ = new Subject();
  // ... do your babel onNext() business
  return {
    DOM: // ...
    logs: error$
  };
}