Update statsd.rb
Update statsd.rb

Added gauge metric.
tinglinux/logstash-kafka,opentable/logstash-kafka,joekiller/logstash-kafka,Aloomaio/logstash-kafka,opentable/logstash-kafka,tinglinux/logstash-kafka,joekiller/logstash-kafka,Aloomaio/logstash-kafka