Update nats readme

plugins/inputs/nats/README.md

-# NATS Monitoring Input Plugin
+# NATS Input Plugin
 
-The [NATS](http://www.nats.io/about/) monitoring plugin reads from
-specified NATS instance and submits metrics to InfluxDB. 
+The [NATS](http://www.nats.io/about/) monitoring plugin gathers metrics from
+the NATS [monitoring http server](https://www.nats.io/documentation/server/gnatsd-monitoring/).
 
-## Configuration
+### Configuration
 
 ```toml
 [[inputs.nats]]
-  ## The address of the monitoring end-point of the NATS server
+  ## The address of the monitoring endpoint of the NATS server
   server = "http://localhost:8222"
+
+  ## Maximum time to receive response
+  # response_timeout = "5s"
+```
+
+### Metrics:
+
+- nats
+  - tags
+    - server
+  - fields:
+    - uptime (integer, nanoseconds)
+    - mem (integer, bytes)
+    - subscriptions (integer, count)
+    - out_bytes (integer, bytes)
+    - connections (integer, count)
+    - in_msgs (integer, bytes)
+    - total_connections (integer, count)
+    - cores (integer, count)
+    - cpu (integer, count)
+    - slow_consumers (integer, count)
+    - routes (integer, count)
+    - remotes (integer, count)
+    - out_msgs (integer, count)
+    - in_bytes (integer, bytes)
+
+### Example Output:
+
+```
+nats,server=http://localhost:8222 uptime=117158348682i,mem=6647808i,subscriptions=0i,out_bytes=0i,connections=0i,in_msgs=0i,total_connections=0i,cores=2i,cpu=0,slow_consumers=0i,routes=0i,remotes=0i,out_msgs=0i,in_bytes=0i 1517015107000000000
 ```

plugins/inputs/nats/nats.go

@@ -25,7 +25,7 @@ type Nats struct {
 
 var sampleConfig = `
   ## The address of the monitoring endpoint of the NATS server
-  server = "http://localhost:1337"
+  server = "http://localhost:8222"
 
   ## Maximum time to receive response
   # response_timeout = "5s"