Update conferences page (it)
Merge pull request #619 from kennyadsl/update_conferences_page_it

Update conferences page (it)
Unify links to rubyconf.org on conferences page
Fix several typos on conferences page (it)
added logger
use passenger
Improve markdown formatting (installation, downloads)

Isolate common content for better diffs between langs.
Use named link references on about page
Add redirection rule: /foo to /foo/ (when /foo/index.html exists)
Fix link on about page (de)
Merge pull request #620 from makimoto/redirection-index-html

Add redirection rule: /foo to /foo/ (when /foo/index.html exists)
Fix typo (ru)

Fixes issue #621, reported by @ap-Codkelden.
Change RoR footnote to normal link on about page

Also add missing links to footnotes for zh_cn.