web site doc: add a reference to GitHub Jekyll usage page.
web site doc: rename page as an attempt to solve #90.
(https://help.github.com/articles/using-jekyll-with-pages suggests name
clash with other projects as one source for the problem)
Recreate web documentation as a Unix file (attempt to fix #90)
Merge pull request #91 from jouvin/jekyll-doc

Web site doc: minor change
Web site doc: remove overlooked conflict