Make the logstash integration testing a gem

The purpose of this PR is to setup the foundations to have the integration testing support for logstash as a gem, there is still some thing that have to be improved, but for now this is able to:

* Provide two commands after the gem installation (lsit-deps and lsit-suite), no lsit-run for now.
* If the config, input and suite definitions are in the same logstash place it just runs the test without problems.

NOTICE: This is mainly a port of what was there but as a gem, next steps are to make this more nice, include more test, reports, to make the config/input/suite easy, etc.. but for now you can start reviewing and merging if good enought
we should be using cabin, but I'll do that in the feature. Should we do it right now?