Set the 'ruby code' encoding for all files to UTF-8. This has the
effect that all string literals are UTF-8 now.

This was achieved with:
sed -i -e '1 { /^# encoding: utf-8/! { i # encoding: utf-8
} }' lib/logstash/**/*.rb
- found some more files that needed to have encoding set.
Merge git://github.com/logstash/logstash