Add more advanced scheduling example #24

Either here or in the tutorial we should add an example of more advanced scheduling, to show why we need the complexity of binding a scheduler.

@yihozhang gave an example like this where you want analysis to not use the backoff (for performance, even though saturating with back-off is the same saturating without it), but the other parts you do want to use the back-off:

(run-schedule
  (let-scheduler bo (back-off))
  (repeat 10
    (saturate analysis)
    (run-with bo optimization)))