Add Kafka 0.9+ consumer support (#2487)

etc/telegraf.conf

@@ -2198,11 +2198,42 @@
 #   ## 0 means to use the default of 65536 bytes (64 kibibytes)
 #   max_line_size = 0
 
-
-# # Read metrics from Kafka topic(s)
+# # Read metrics from Kafka 0.9+ topic(s)
 # [[inputs.kafka_consumer]]
 #   ## topic(s) to consume
 #   topics = ["telegraf"]
+#   ## kafka servers
+#   brokers = ["localhost:9092"]
+#   ## the name of the consumer group
+#   consumer_group = "telegraf_metrics_consumers"
+#   ## Offset (must be either "oldest" or "newest")
+#   offset = "oldest"
+#
+#   ## Optional SSL Config
+#   # ssl_ca = "/etc/telegraf/ca.pem"
+#   # ssl_cert = "/etc/telegraf/cert.pem"
+#   # ssl_key = "/etc/telegraf/key.pem"
+#   ## Use SSL but skip chain & host verification
+#   # insecure_skip_verify = false
+#
+#   ## Optional SASL Config
+#   # sasl_username = "kafka"
+#   # sasl_password = "secret"
+#
+#   ## Data format to consume.
+#   ## Each data format has its own unique set of configuration options, read
+#   ## more about them here:
+#   ## https://github.com/influxdata/telegraf/blob/master/docs/DATA_FORMATS_INPUT.md
+#   data_format = "influx"
+#
+#   ## Maximum length of a message to consume, in bytes (default 0/unlimited);
+#   ## larger messages are dropped
+#   max_message_len = 65536
+
+# # Read metrics from Kafka (0.8 or less) topic(s)
+# [[inputs.kafka_consumer_legacy]]
+#   ## topic(s) to consume
+#   topics = ["telegraf"]
 #   ## an array of Zookeeper connection strings
 #   zookeeper_peers = ["localhost:2181"]
 #   ## Zookeeper Chroot