Use extend when you mean it and don't fake it with include
Reduce the number of method calls
Reuse the logger code of base Ruby 2.0.0
Use log formatters to format individual log lines
Simplify logstash_event call
Pass whole configuration hash to Rackstash.setup
Completely remove the ZMQ logger.

It naver worked reliably and often would crash the Rails process
because of zmq's inability to deal with threads and forks.
It seems much more reliable, to just log to a file and to feed that
file directly into logstash.