Node 6.0 incompatibility

[pcottle]

We seem to be getting an error from within grunt-hash for Node 6.2.0+ builds, saying:

Warning: Path must be a string. Received undefined

More context over here: https://github.com/pcottle/learnGitBranching/issues/392

Is there any remedy we can add from the Grunt config options? cc @bitwiseman

[lhtdesignde]

any change this gets fixed soon? running into the same problem and I can't downgrade node. running node 6.4.0