I forked the source code for website from arquillian - code.
It uses several technologies under the hood - starting from Ruby, Bootstrap-sass, HAML and end awestruct.
HAML can interpret textile fragments. Recently, however, the textile and maruku plugin filters have been moved to another gem - haml-contrib.
After installing ruby 1.9.3 and haml with haml-contrib I received the following error when interpreting *.haml files with the ":textile" fragment:
> haml test.html.haml
Haml error on line 261: To use the "textile" filter, please install the haml-contrib gem.
Use --trace for backtrace.
I tested the application on Ubuntu 12.10. The only way I got it to work is when I compiled yaml, ruby and rubygems from source. The following tutorial from CentOS should be of help: