Initial setup for Vietnamese translation of site (vi)

Provides

* the site root page (index.html),
* the news.rss file, and
* the examples directory

Also adapts Rakefile.
Add vi support for _config.yml
Translate examples and /index.html (vi)
Fix example; add newline (vi)
Translate 'about' and 'downloads' page (vi)
Small fixes on 'about' and 'downloads' page (vi)
Translate 'libraries' and 'security' pages (vi)
Small fixes on libraries page (vi)
Update security page (vi)
Translate community pages (vi)
Translate all 2013-06 posts [vi]
Fix community pages (vi)

Fix typo, remove trailing whitespace, add newlines, rewrap,
fix indentation style.
Translation Documentation/Success Stories [vi]
Merge pull request #247 from joneslee85/vi-translation-5

Translate all 2013-06 posts [vi]
Fix links to translated CVE-2013-4073 post (vi)
Fix typos in news posts (vi)
Fix style in news posts: rewrap, newlines (vi)
Translate documentation page and quickstart (vi)
Fix typos and wrong markdown (vi)
Fix markdown indentation and rewrap (vi)