Dockerize your hugo

I like to automate when I can. Sometimes it is it boring stuff, sometimes it's for the fun of figuring it out. When I first started using hugo I found that having the latest hugo installed on each of my machines was, at times, a tiresum exercise when all I wanted to do was write a post. So, I made a custom docker image and makefile to automate it. If I want to build the latest hugo, I run make hugo.