Install Gollum Wiki on Ubuntu

In this tutorial, we will explain how to install Gollum Wiki on an Ubuntu 16.04 VPS with Puma and Nginx. Gollum is a simple open source wiki system built on top of Git. A Gollum Wiki is a git repository with pages organized into directories any way you choose. This guide should work on other Linux VPS systems as well but was tested and written for Ubuntu 16.04 VPS.