To create the base image with Wesnoth's dependencies:
docker build -t wesnoth:16.04 -f docker/Dockerfile-base docker
To create the image that travis will run during a build:
docker build -t wesnoth-repo:16.04 -f docker/Dockerfile-travis .
To push a new base image to Docker Hub
docker login Username: wesnoth
docker tag <Image ID from docker images> wesnoth/wesnoth:16.04
docker push wesnoth/wesnoth:16.04