Clarify output format for splunkmetric

(cherry picked from commit 146a30e)

Author: danielnelson

plugins/serializers/splunkmetric/README.md

@@ -1,12 +1,11 @@
 # Splunk Metrics serializer
 
-This serializer formats and outputs the metric data in a format that can be consumed by a Splunk metrics index.
-It can be used to write to a file using the file output, or for sending metrics to a HEC using the standard telegraf HTTP output.
+The Splunk Metrics serializer outputs metrics in the [Splunk metric HEC JSON format][splunk-format].
 
+It can be used to write to a file using the file output, or for sending metrics to a HEC using the standard telegraf HTTP output.
 If you're using the HTTP output, this serializer knows how to batch the metrics so you don't end up with an HTTP POST per metric.
 
-Th data is output in a format that conforms to the specified Splunk HEC JSON format as found here:
-[Send metrics in JSON format](http://dev.splunk.com/view/event-collector/SP-CAAAFDN).
+[splunk-format]: http://dev.splunk.com/view/event-collector/SP-CAAAFDN#json
 
 An example event looks like:
 ```javascript