Add documentation for Riemann sink.

Signed-off-by: Vishnu kannan <vishnuk@google.com>

docs/sink-configuration.md

@@ -88,7 +88,7 @@ To use the kafka sink add the following flag:
 
 Normally, kafka server has multi brokers, so brokers' list need be configured for producer.
 So, we can set `KAFKA_SERVER_URL` to a dummy value, and provide kafka brokers' list in url's query string.
-Besides,the following options need be set in query string:
+Besides, the following options can be set in query string:
 
 * `timeseriestopic` - Kafka's topic for timeseries. Default: `heapster-metrics`
 * `eventstopic` - Kafka's topic for events. Default: `heapster-events`
@@ -97,6 +97,19 @@ Like this:
 
     --sink="kafka:?brokers=0.0.0.0:9092&brokers=0.0.0.0:9093"
 
+### Riemann
+This sink supports metrics and events.
+To use the reimann sink add the following flag:
+
+	--sink="riemann:<RIEMANN_SERVER_URL>[?<OPTIONS>]"
+
+The following options are available:
+
+* `ttl` - TTL for writes to Riemann. Default: `60 seconds`
+* `state` - FIXME. Default: `""`
+* `tags` - FIXME. Default. `none`
+* `storeEvents` - Control storage of events. Default: `true`
+
 ## Modifying the sinks at runtime
 
 Using the `/api/v1/sinks` endpoint, it is possible to fetch the sinks