NodeJS - Add post install `npm update -g`

NodeJS is no longer bundling an up to date NPM package, currently shipping with v1.4.28, now post install running `npm update -g` will update to NPM v2.1.10 at time of writing.

Note: After "Travelling Directories" are implemented this would also then update all NPM "Global" packages, not sure this is a bad thing but worth noting.