It seems like based on the article you linked your best course of action would be:
sudo chown -R $(whoami) $(npm config get prefix)/{lib/node_modules,bin,share}

Also in the future I would recommend using n installable via sudo npm install -g n and you can switch to for example Node 4.5 using n 4.5 I’ve seen a lot of people have permission problems after using nvm. Not to say they haven’t fixed it more recently :)