Online webite: https://programming-contest.github.io developed by https://jekyllrb.com/.
Used Versions:
$ ruby --version
ruby 2.4.1p111 (2017-03-22 revision 58053) [x86_64-linux]
$ bundle exec jekyll serve
...
Server address: http://127.0.0.1:4000/
Server running... press ctrl-c to stop.
...
Go to your favorite browser at http://127.0.0.1:4000/.
https://jekyllrb.com/
https://help.github.com/articles/setting-up-your-github-pages-site-locally-with-jekyll/