Make nokogiri use the bundled version of libxml2 instead of the system
version. In the past installing nokogiri was slow because it had to
compile the bundled version of libxml2, which is partly why we switched
to the system library. Now it's faster because the bundled version comes
pre-compiled with the nokogiri gem.
https://nokogiri.org/#native-gems-faster-more-reliable-installation
Reverts 440bbbb28.
Docker
This directory contains files for building Docker images for Danbooru.