Fix 404 when logging into Docker

.travis.yml

@@ -46,7 +46,7 @@ before_deploy:
   - git config --local user.name "$USER_NAME"
   - git config --local user.email "$USER_EMAIL"
   - if ! git tag "$TAG" "$TRAVIS_COMMIT" ; then echo "$TAG already exists"; fi
-  - if [[ -n "$DOCKER_BUILD" ]] ; then echo "$DOCKER_PASSWORD" | docker login -u "$DOCKER_USERNAME" --password-stdin hub.docker.com ; fi
+  - if [[ -n "$DOCKER_BUILD" ]] ; then echo "$DOCKER_PASSWORD" | docker login -u "$DOCKER_USERNAME" --password-stdin ; fi
 
 deploy:
   - provider: releases