Fix deploy script (#173)

Fix the deploy script and deploy script and push rolling releases only when cron jobs run.

.travis/deploy_dockerhub.sh

@@ -1,10 +1,18 @@
 #!/bin/sh
 
-if [[ "$TRAVIS_BRANCH" == "master" ]]
-then
-	docker login -e $DOCKER_EMAIL -u $DOCKER_USER -p $DOCKER_PASS
-	docker push maxking/mailman-web
-	docker push maxking/mailman-core
+function deploy {
+		docker login -e $DOCKER_EMAIL -u $DOCKER_USER -p $DOCKER_PASS
+		docker push maxking/mailman-web:$1
+		docker push maxking/mailman-core:$1
+}
+
+
+if [ "$TRAVIS_EVENT_TYPE" = "cron" ]; then
+		deploy "rolling"
+elif [ "$TRAVIS_BRANCH" = "master" ]; then
+		deploy "latest"
 else
-	echo "Non-master branch aren't pushed to DockerHub..."
+		# If the branch isn't master and this was not a cron job, no need to deploy.
+		echo "TRAVIS_EVENT_TYPE = $TRAVIS_EVENT_TYPE, TRAVIS_BRANCH = $TRAVIS_BRANCH"
+		exit 0
 fi