Change the prerequisites for Ubuntu

[gilbertfl]

The prerequisites in the setup page uses cUrl to change the node.js+npm version.

This locks the system to the version, and the syntax is unnecessarily complicated. Also, apt panics and aborts system updates because node.js is in some dev version.

Maybe use nvm or some other tool that does not panic apt when Ubuntu tries to install updates.

[gilbertfl]

As a side-quest, add yarn in the setup page.
sudo npm install -g yarn

[gilbertfl]

nvm is the official node.js version manager. Same timeline, great choice. Repo for nvm