Upgrade NodeJS

[fofr]

We'd like to start linting our Javascript using standard, see:
https://standardjs.com/
alphagov/govuk-lint#63
alphagov/govuk_frontend_toolkit#334

To run standard linting on our VMs and on Jenkins we need a modern version of NodeJS (> 4). We currently run version 0.10, which hasn't been updated since 2015:

govuk-puppet/hieradata/common.yaml

Line 1150 in a6c51d8

nodejs::version: '0.10.37-1chl1~%{::lsbdistcodename}1'

009e0b1

The PR that updated Node mentioned StatsD and Performance Platform as dependencies. Is that still the case?

cc @boffbowsh

[fofr]

This might be the time to include something like nvm too. https://github.com/creationix/nvm