Async 1.4.2 vunerabilities

[sf0rman]

Gemnasium scanner reports: "A vulnerability exists in Async through 3.2.1 (fixed in 3.2.2), which could let a malicious user obtain privileges via the mapValues() method."

I cloned the repo locally and updated the dependency, all unit tests seem to work so hopefully no code changes required if you do this (although I didn't test it thoroughly).