Integration test backported to v1.4.2

Ported the integration test code, original created by @colinsurprenant to the 1.4.x branch. 

There is a little change in this PR, regarding the original code for the 1.5 version, and thats is the removal of the 2>&1 option in the command issued to start the logstash instance. Even if this works with 1.5, its is not with 1.4.2 but I'm not sure why it happens.