Use notifySubscribers instead of subscribe to do rate-limiting. This doesn't properly handle the deferEvaluation tests.
Fix initialization of "deferEvaluation" computed observable.
Replace notifySubscribers in the limit function instead of having extra login in the normal notifySubscribers.
Make limit function private; take out "funcOptions" and use anonymous function instead; don't pass "target" to the callback.

Add tests showing behavior of multiple calls to rateLimit.