Get rid of node-hashes

[akshat1]

node-hashes uses node-gyp and is often problematic in CI environments. It won't work on Travis which is stuck on node 6, and it won't work on my own jenkins unless build-essential is installed; and then it will throw warnings about deprecated C++.

Considering we only use JSHashes, it might be a good idea to simply extract this function in a pure JS module and use that.