Add burrow input plugin (#3489)

plugins/inputs/burrow/README.md

@@ -0,0 +1,98 @@
+# Telegraf Plugin: Burrow
+
+Collect Kafka topic, consumer and partition status
+via [Burrow](https://github.com/linkedin/Burrow) HTTP [API](https://github.com/linkedin/Burrow/wiki/HTTP-Endpoint).
+
+Supported Burrow version: `1.x`
+
+### Configuration
+
+```
+  ## Burrow API endpoints in format "schema://host:port".
+  ## Default is "http://localhost:8000".
+  servers = ["http://localhost:8000"]
+
+  ## Override Burrow API prefix.
+  ## Useful when Burrow is behind reverse-proxy.
+  # api_prefix = "/v3/kafka"
+
+  ## Maximum time to receive response.
+  # response_timeout = "5s"
+
+  ## Limit per-server concurrent connections.
+  ## Useful in case of large number of topics or consumer groups.
+  # concurrent_connections = 20
+
+  ## Filter clusters, default is no filtering.
+  ## Values can be specified as glob patterns.
+  # clusters_include = []
+  # clusters_exclude = []
+
+  ## Filter consumer groups, default is no filtering.
+  ## Values can be specified as glob patterns.
+  # groups_include = []
+  # groups_exclude = []
+
+  ## Filter topics, default is no filtering.
+  ## Values can be specified as glob patterns.
+  # topics_include = []
+  # topics_exclude = []
+
+  ## Credentials for basic HTTP authentication.
+  # username = ""
+  # password = ""
+
+  ## Optional SSL config
+  # ssl_ca = "/etc/telegraf/ca.pem"
+  # ssl_cert = "/etc/telegraf/cert.pem"
+  # ssl_key = "/etc/telegraf/key.pem"
+  # insecure_skip_verify = false
+```
+
+### Partition Status mappings
+
+* `OK` = 1
+* `NOT_FOUND` = 2
+* `WARN` = 3
+* `ERR` = 4
+* `STOP` = 5
+* `STALL` = 6
+
+> unknown value will be mapped to 0
+
+### Fields
+
+* `burrow_group` (one event per each consumer group)
+  - status (string, see Partition Status mappings)
+  - status_code (int, `1..6`, see Partition status mappings)
+  - parition_count (int, `number of partitions`)
+  - total_lag (int64, `totallag`)
+  - lag (int64, `maxlag.current_lag || 0`)
+
+* `burrow_partition` (one event per each topic partition)
+  - status (string, see Partition Status mappings)
+  - status_code (int, `1..6`, see Partition status mappings)
+  - lag (int64, `current_lag || 0`)
+  - offset (int64, `end.timestamp`)
+  - timestamp (int64, `end.timestamp`)
+
+* `burrow_topic` (one event per topic offset)
+  - offset (int64)
+
+
+### Tags
+
+* `burrow_group`
+  - cluster (string)
+  - group (string)
+
+* `burrow_partition`
+  - cluster (string)
+  - group (string)
+  - topic (string)
+  - partition (int)
+
+* `burrow_topic`
+  - cluster (string)
+  - topic (string)
+  - partition (int)