Tavis-ci to upload images to the Docker hub, after succesfull tests.

For this to work, the following variables will need to be set at Docker hub:
 - DOCKER_ORG	first part of docker repo name (example: mailu)
 - DOCKER_UN	Docker-hub login username (private)
 - DOCKER_PW	Docker-hub login password (private)
Note that also Docker hub autobuilds will have to be disabled.

.travis.yml

@@ -11,3 +11,7 @@ script:
   - docker-compose -f tests/build.yml -p Mailu build
   - tests/compose/test-script.sh
 
+deploy:
+  provider: script
+  script: bash tests/deploy.sh
+