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.