use github actions CI

- remove travis-ci.yml
- remove comments from main workflow

.github/workflows/main.yml

@@ -1,9 +1,5 @@
 name: Main
 on:
-  # push:
-  #   branches:
-  #     - master # should run docker-push when no pull request
-  # create: # should run docker-tag when it is a tag, and no pull request
   release:
     types: [published]
 

.travis.yml

@@ -1,63 +0,0 @@
-language: java
-
-jdk:
-    - openjdk8
-
-services:
-    - docker
-
-dist: xenial
-
-os: linux
-
-stages:
-  - build
-  - name: docker-tag
-    if: (tag IS present) AND (type != pull_request)
-  - name: docker-push
-    if: (branch = master) AND (type != pull_request)
-
-jobs:
-    include:
-        - stage: build
-          name: war
-          script: mvn --batch-mode --define java.net.useSystemProxies=true package
-          before_deploy: cp target/plantuml.war target/plantuml-${TRAVIS_BRANCH}.war
-          deploy:
-              provider: releases
-              token: "$GITHUB_TOKEN"
-              file: "target/plantuml-${TRAVIS_BRANCH}.war"
-              skip_cleanup: true
-              on:
-                  tags: true
-
-        - stage: docker-tag
-          name: jetty-tag
-          script:
-              - if [ -z "$TRAVIS_TAG" ]; then exit 0; fi
-              - docker login  -u $DOCKER_LOGIN -p $DOCKER_PASSWORD
-              - docker build --pull -t plantuml/plantuml-server:jetty-$TRAVIS_TAG -f Dockerfile.jetty .
-              - docker push plantuml/plantuml-server:jetty-$TRAVIS_TAG
-
-        - stage: docker-tag
-          name: tomcat-tag
-          script:
-              - if [ -z "$TRAVIS_TAG" ]; then exit 0; fi
-              - docker login  -u $DOCKER_LOGIN -p $DOCKER_PASSWORD
-              - docker build --pull -t plantuml/plantuml-server:tomcat-$TRAVIS_TAG -f Dockerfile.tomcat .
-              - docker push plantuml/plantuml-server:tomcat-$TRAVIS_TAG
-
-        - stage: docker-push
-          name: jetty-push
-          script:
-              - docker login  -u $DOCKER_LOGIN -p $DOCKER_PASSWORD
-              - docker build --pull -t plantuml/plantuml-server:jetty -f Dockerfile.jetty .
-              - docker tag plantuml/plantuml-server:jetty plantuml/plantuml-server:latest
-              - docker push plantuml/plantuml-server:jetty
-              - docker push plantuml/plantuml-server:latest
-        - stage: docker-push
-          name: tomcat-push
-          script:
-              - docker login  -u $DOCKER_LOGIN -p $DOCKER_PASSWORD
-              - docker build --pull -t plantuml/plantuml-server:tomcat -f Dockerfile.tomcat .
-              - docker push plantuml/plantuml-server:tomcat