update node.js for macos code example

Example 1: update nodejs mac

sudo npm cache clean -f 
sudo npm install -g n
sudo n stable/lts

Example 2: update to node 12 mac

// Fix node not found first	
sudo chown -R `whoami`:admin /usr/local/include/node
    sudo chown -R `whoami`:admin /usr/local/bin
    sudo chown -R `whoami`:admin /usr/local/share
    sudo chown -R `whoami`:admin /usr/local/lib/dtrace 

 brew link --overwrite node
 
// Then: 
sudo npm cache clean -f 
sudo npm install -g n 
sudo n stable/lts