General problems with jekyll back-end

[fsimonis]

We are increasingly facing issues with jekyll and the plugins we need, some of which unmaintained.
This has reached the point where every time I want to build the website locally, I need to debug first.

The problems dependencies of the website are as follows:

• jekyll-sass-converter, a core dependency of jekyll, either depends on the broken sassc ruby or on google-protobuf, which fails to compile on systems that use link-time optimization by default such as Arch or Fedora. This is an unfixed long-known issue with the gem.
• jekyll-algolia has been abandoned by algolia.
• jekyll-last-modified-at depends on posix-spawn which is unmaintained and needs to be patched via a PR.
• open-uri from the citation generator depends on stringio which occasionally fails to compile on some systems.