There are no installation instructions for Ubuntu 18.04 in the README

Ghost User
2018-10-14T20:43:50+02:00

Add installation instructions for Ubuntu 18.04

### Why?
Ubuntu 18.04 is the newest version.

### Current implementation
There are no installation instructions for Ubuntu 18.04 in the README.

### Desired implementation
There are installation instructions for Ubuntu 18.04 in the README.