Update dependencies

Outdated Dev Dependencies prior to this set of changes:

grunt-contrib-clean (package: ^0.5.0, latest: 0.6.0)
grunt-contrib-jshint (package: ^0.9.2, latest: 0.10.0)
grunt-contrib-nodeunit (package: ^0.3.3, latest: 0.4.1)

As we haven't published an update to the package for a few months, it may be worth doing so if/after we land the changes here.