Optimize Sleep Time for Multiple Limits

[deckar01]

Chaining limits causes waiting processes to wake early and churn.

[deckar01]

The RateLimitDecorator could inspect the func in __call__ and determine if it is a compatible wrapper with attributes like __func__ and __limits__. It could then discard the previously wrapped func, wrap the original __func__, and append the previous __limits__ to its own instance. Then sleep time can be computed as the maximum period remaining of all limits.