Removed superfluous variables.
Improved documentation
Fixed state variables and how they’re populated
Merge branch 'master' of https://github.com/logstash/logstash

# By Jordan Sissel (2) and Kurt Hurtado (2)
# Via Jordan Sissel (2) and Kurt Hurtado (2)
* 'master' of https://github.com/logstash/logstash:
  adding COMMONAPACHELOG
  Update jruby version
  Update jruby version
  Adding COMMONAPACHELOG format
Fixes to address issues raised in comments to PR.

Prune empty fields `plugin_instance` and `type_instance` only, instead of crawling through entire hash looking for empty values.
Simplified iterating through values
Fix empty string vs. nil check.
Cleaned up syntax of some conditionals.
Merge pull request #804 from untergeek/master

Updated collectd plugin to fix and streamline it