add graylog plugin

add unit test for graylog

plugins/inputs/graylog/README.md

@@ -0,0 +1,46 @@
+# GrayLog plugin
+
+The Graylog plugin can collect data from remote Graylog service URLs. 
+
+Plugin currently support two type of end points:-
+
+- multiple  (Ex http://[graylog-server-ip]:12900/system/metrics/multiple)
+- namespace (Ex http://[graylog-server-ip]:12900/system/metrics/namespace/{namespace})
+
+End Point can be a mixe of one  multiple end point  and several namespaces end points
+
+
+Note: if namespace end point specified metrics array will be ignored for that call.
+
+Sample configration
+```
+[[inputs.graylog]]
+  ## API End Point, currently supported API:
+  ## - multiple  (Ex http://[graylog-server-ip]:12900/system/metrics/multiple)
+  ## - namespace (Ex http://[graylog-server-ip]:12900/system/metrics/namespace/{namespace})
+  ## Note if namespace end point specified metrics array will be ignored for that call.
+  ## End point can contain namespace and multiple type calls
+  ## Please check http://[graylog-server-ip]:12900/api-browser for full list end points
+
+  servers = [
+    "http://10.224.162.16:12900/system/metrics/multiple"
+  ]
+
+  #Metrics define metric which will be pulled from GrayLog and reported to the defined Output 
+  metrics = [
+    "jvm.cl.loaded",
+    "jvm.memory.pools.Metaspace.committed"
+  ]
+  ## User name and password  
+  username = "put-username-here"
+  password = "put-password-here"
+
+  ## 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
+```
+
+Please refer to GrayLog metrics api browser for full metric end points http://10.224.162.16:12900/api-browser