Better algorithm for checking

[vutran1710]

The current algorithm (On) is just good for limiting rate using bucket with cap of hundred items. When the ratelimit is something like 20k/months, the algo would make the acquiring process painfully show. Therefore a better algo is needed.

[vutran1710]

Complexity is now reduced to

• O(logn) for insert (include checking + insertion)
• O(n) for leaking
• O(1) for removing