Monkey patch the gem_publisher execute method in jruby
Monkey patch the gem_publisher execute method in jruby

This is due to a bug in JRuby's Open3.capture3 method.
Using Open3.popen3 solves the problem

Fixes #2

guyboertje/logstash-devutils,jsvd/logstash-devutils,elastic/logstash-devutils,ph/logstash-devutils,Mogztter/logstash-devutils