Drop rails_12factor gem

Use the proposed rails 5 environment variables instead.

config/environments/production.rb

@@ -43,10 +43,17 @@ Osem::Application.configure do
   config.log_level = ENV['OSEM_LOG_LEVEL'].try(:to_sym) || :info
 
   # Prepend all log lines with the following tags
-  # config.log_tags = [ :subdomain, :uuid ]
+  config.log_tags = [:uuid]
 
-  # Use a different logger for distributed setups
-  # config.logger = ActiveSupport::TaggedLogging.new(SyslogLogger.new)
+  # Disable serving static files from the `/public` folder by default since
+  # Apache or NGINX already handles this.
+  config.public_file_server.enabled = ENV['RAILS_SERVE_STATIC_FILES'].present?
+
+  if ENV["RAILS_LOG_TO_STDOUT"].present?
+    logger           = ActiveSupport::Logger.new(STDOUT)
+    logger.formatter = config.log_formatter
+    config.logger = ActiveSupport::TaggedLogging.new(logger)
+  end
 
   # Use a different cache store in production
   # config.cache_store = :mem_cache_store