Added Gemfile for managing dependencies through bundler.
Added Rakefile.
Added task for checking external links.
Added screenshot CSS class.
Added plain text link support to git link filter.
Get rid of external /files links.
Assorted small changes.

Don't generate comments by default.
Support 'plain' pages without layout through no_default_layout.
Generate feed as .html instead of .xml for constrained servers.
Added 'update_software' task to generate software pages.

The pages are generated from the README files from the Git
repositories of the projects.
Updated README.