update the node js version in ubuntu code example

Example 1: update nodejs

//First, clear the npm cache:
	npm cache clean -f

//Install n, Node’s version manager:
	npm install -g n
    
//With the n module installed, you can use it to:
	Install the latest stable version: n stable
	Install the latest release: n latest

Example 2: how to upgrade to latest node in ubuntu 17.04 using terminal

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