Add recommended min Node.js version
Add recommended min Node.js version

Node.js version 'recommended for most users' is currently v4.5.0 LTS. Workshopper menu selection bug (see Node.js issue [#5384](https://github.com/nodejs/node/issues/5384)) fixed in v6.2.0, so current version is recommended for NodeSchool users.
nodeschool/nodeschool.github.io,nodeschool/nodeschool.github.io,nodeschool/nodeschool.github.io