Add an include for unmaintained translations
Enable including extra content on homepage

Include (extra) content specified in the /??/index.html file
at the top of the generated homepage. Currently only meant
for an "unmaintained translation" message.
Mark bg, ko, pt, tr as unmaintained
Move inline CSS to stylesheet
Merge pull request #333 from ruby/unmaintained-include

Provide an "unmaintained" message for abandoned translations