Update note on arguments leaking deoptimization

Author: aduth

README.md

@@ -110,7 +110,7 @@ Memize creates a [last-in first-out stack](https://en.wikipedia.org/wiki/Stack_(
 
 Each node in the list tracks the original arguments as an array. This acts as a key of sorts, matching arguments of the current invocation by performing a shallow equality comparison on the two arrays. Other memoization implementations often use `JSON.stringify` to generate a string key for lookup in an object cache, but this benchmarks much slower than a shallow comparison ([jsperf](https://jsperf.com/lookup-json-stringify-vs-shallow-equality)).
 
-Finally, special care is made toward treatment of `arguments` due to engine-specific deoptimizations which can occur in V8 via [arguments leaking](https://github.com/petkaantonov/bluebird/wiki/Optimization-killers#3-managing-arguments). Order is important here; we only create a shallow clone when necessary, after the cache has been checked, to avoid creating a clone unnecessarily if a cache entry exists. Looking at the code, you'd not be blamed for thinking that dropping the shallow clone would improve performance, but in fact it would _slow_ execution by approximately 60%. This is due to how the lingering `arguments` reference would carry over by reference ("leaks") in the node's `args` property.
+Finally, special care is made toward treatment of `arguments` due to engine-specific deoptimizations which can occur in V8 via [arguments leaking](https://github.com/petkaantonov/bluebird/wiki/Optimization-killers#3-managing-arguments). Order is important here; we only create a shallow clone when necessary, after the cache has been checked, to avoid creating a clone unnecessarily if a cache entry exists. Looking at the code, you'd not be blamed for thinking that dropping the shallow clone would improve performance, but in fact it would _slow_ execution by approximately 60%. This is due to how the lingering `arguments` reference would carry over by reference ("leaks") in the node's `args` property. _**Update:** As of November 2019, engine improvements are such that `arguments` leaking does not have as dramatic an effect. However, my testing shows that the shallow clone still performs equal or better than referencing `arguments` directly, and as such the implementation has not been revised in order to achieve optimal performance in the most versions of V8._
 
 ## License