Unreleased

• Fixes stringify to only take ancestors into account when checking
  circularity.
  It previously assumed every visited object was circular which led to false
  positives.
  Uses the tiny serializer I wrote for Must.js a year and a half ago.
• Fixes calling the replacer function in the proper context (thisArg).
• Fixes calling the cycleReplacer function in the proper context (thisArg).
• Speeds serializing by a factor of
  Big-O(h-my-god-it-linearly-searched-every-object) it had ever seen. Searching
  only the ancestors for a circular references speeds up things considerably.