message: add some echo to docker.sh
diff: if [ "$TRAVIS_BRANCH" == "master" ] || [ "$TRAVIS_BRANCH" == "develop" ]; then
  if [ "$TRAVIS_PULL_REQUEST" == "false" ]; then
  + echo "build docker images";
  docker build -t hdafbi/geli-api:latest -f .docker/api/Dockerfile .
  docker tag hdafbi/geli-api hdafbi/geli-api:$TRAVIS_BRANCH
  docker build -t hdafbi/geli-web-frontend:latest -f .docker/web-frontend/Dockerfile .
  docker tag hdafbi/geli-web-frontend hdafbi/geli-web-frontend:$TRAVIS_BRANCH
  + echo "publish docker images";
  docker login -u="$DOCKER_USERNAME" -p="$DOCKER_PASSWORD";
  docker push hdafbi/geli-api;
  docker push hdafbi/geli-api:$TRAVIS_BRANCH;
  docker push hdafbi/geli-web-frontend;
  docker push hdafbi/geli-web-frontend:$TRAVIS_BRANCH;
  + else
  + echo "omit docker build and publish. (pull request: #$TRAVIS_PULL_REQUEST)";
  fi
  +else
  + echo "omit docker build and publish. (wrong branch: $TRAVIS_BRANCH)";
  fi
  