CD Improvement

To push the latest tag as a docker image tagged like:
- Exact tag, f.e. `:3.0.3`
- Latest tag, `:latest`
- Latest minor release, f.e. `:3.0` 
- Latest major release, f.e. `:3`

.travis.yml

@@ -13,6 +13,9 @@ after_success:
 - docker tag ${TRAVIS_COMMIT} killrvideo/killrvideo-generator:${TRAVIS_TAG}
 - docker login -u $DOCKER_USER -p $DOCKER_PASS
 - docker push killrvideo/killrvideo-generator:${TRAVIS_TAG}
+- "[ \"$(git tag --sort=-v:refname | grep -P \"^\\d+.\\d+.\\d+$\" | head -n1)\" == \"$TRAVIS_TAG\" ] && { docker tag ${TRAVIS_COMMIT} killrvideo/killrvideo-generator:latest; docker push killrvideo/killrvideo-generator:latest; }"
+- "[ \"$(git tag --sort=-v:refname | grep -P \"^\\d+.\\d+.\\d+$\" | head -n1)\" == \"$TRAVIS_TAG\" ] && { docker tag ${TRAVIS_COMMIT} killrvideo/killrvideo-generator:$(echo $TRAVIS_TAG | cut -d'.' -f 1); docker push killrvideo/killrvideo-generator:$(echo $TRAVIS_TAG | cut -d'.' -f 1); }"
+- "[ \"$(git tag --sort=-v:refname | grep -P \"^\\d+.\\d+.\\d+$\" | head -n1)\" == \"$TRAVIS_TAG\" ] && { docker tag ${TRAVIS_COMMIT} killrvideo/killrvideo-generator:$(echo $TRAVIS_TAG | cut -d'.' -f 1).$(echo $TRAVIS_TAG | cut -d'.' -f 2); docker push killrvideo/killrvideo-generator:$(echo $TRAVIS_TAG | cut -d'.' -f 1).$(echo $TRAVIS_TAG | cut -d'.' -f 2); }"
 
 # Sudo required for doing docker build
 sudo: required