Merge pull request #804 from untergeek/master

Updated collectd plugin to fix and streamline it
Have 'release version' computation include the git hash only on .dev
versions
Invoke jruby compilation from ruby code, not via jrubyc

This prevents 'java -jar jruby.jar -S jrubyc' from running something
from $PATH which breaks because jruby expects ruby code and rvm provides
a bash script in its place.
Merge pull request #811 from logstash/better-jrubyc-invocation

Invoke jruby compilation from ruby code, not via jrubyc
Merge pull request #810 from logstash/improve-version-label

Have 'release version' computation include the git hash only on .dev
Merge branch 'master' of https://github.com/logstash/logstash

# By Jordan Sissel
# Via Jordan Sissel (3) and Aaron Mildenstein (1)
* 'master' of https://github.com/logstash/logstash:
  Invoke jruby compilation from ruby code, not via jrubyc
  Have 'release version' computation include the git hash only on .dev versions