EXPERIMENTAL: Allow logs to be shipped via different methods.

See https://github.com/dwbutler/logstash-logger#uri-configuration for
a list of available methods.

config/unicorn.conf.rb

@@ -1,10 +1,8 @@
 # See http://unicorn.bogomips.org/Unicorn/Configurator.html
 
-if ENV["UNICORN_JSON_LOG_FORMAT"]
-  unicorn_logger = Logger.new($stderr)
-  require_relative '../lib/unicorn/unicorn_json_log_formatter'
-  unicorn_logger.formatter = UnicornJSONLogFormatter.new
-  logger unicorn_logger
+if ENV["LOGSTASH_URI"]
+  require_relative '../lib/discourse_logstash_logger'
+  logger DiscourseLogstashLogger.logger(uri: ENV['LOGSTASH_URI'], type: :unicorn)
 end
 
 # enable out of band gc out of the box, it is low risk and improves perf a lot