 Update windows install Docs sample output version to indicate that Node 8 is now “ recommended for most users”

https://nodejs.org/en/ currently says  node 8.11 is recommended, but the windows install docs at http://docs.railsbridge.org/installfest/windows suggest that the user will end up with node 6.x.

If node 8 actually works, we should update the docs to list 8.x as the expected sample output.