Fixes stringify to only take ancestors into account when checking
circularity.
It previously assumed every visited object was circular which led to [false
positives][issue9].
Uses the tiny serializer I wrote for [Must.js][must] 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.