Add dockerfile

[viktorstrate]

Add Docker support. This file will download dependencies and install shiori inside an image. This is extremely useful for server maintainers, because it's secure and easy.

Run docker build -t shiori . to build the image
Run docker run -p 8080:8080 -d --rm --name shiori shiori to start a docker container
Run docker exec shiori shiori <COMMAND> to interact with the container

[maxmeyer]

#27 and #11 trying to solve the same problem.

[maxmeyer]

As written in #27: I suggest to use multi stage builds instead: https://docs.docker.com/develop/develop-images/multistage-build/#name-your-build-stages. There's no need for a full "go"-aware alpine image for that. The link contains a suggestion about how to build go projects with that docker feature.

[viktorstrate]

I don't know much about Go. And I made a dockerfile for my own needs, and thought I would share it with you. But I do not know enough about Go to improve it.

Please see #27 for a better implementation