Now that we have a Dockerfile it would be nice to setup an automated build to Docker hub.

That way people don't have to build the image themselves but can simply run docker run stringer/stringer.

Setting this up should be pretty simple, steps are outlined at https://docs.docker.com/docker-hub/builds/#create-an-automated-build. However I do think it needs to be done by the repository owner, or perhaps a collaborator. @swanson or @gabrielpoca could one of you have a look at this?