Merge branch '11-update-baseimage-version' into 'develop'

feat: bump baseimage and bundler

See merge request !24

.gitlab-ci.yml

 # In case something goes horribly wrong, you can fall back to `image: ruby:latest`
-image: git-r3lab.uni.lu:4567/r3/docker/jekyll-lcsb:1.4
+image: git-r3lab.uni.lu:4567/r3/docker/jekyll-lcsb:1.7
 
 build the website:
   stage: build
   before_script:
-  - gem install bundler -v2.0.2
+  - gem install bundler -v2.1.4
   - bundle install && bundle update jekyll-theme-lcsb-default && bundle update jekyll-theme-lcsb-frozen-components
   script:
   - 'echo "baseurl: /$CI_PROJECT_NAME" >> _config_ci.yml'