Add docker hub link.

Author: gorzell

README.md

@@ -9,6 +9,9 @@ At [Keen](http://keen.io) we run some Redis instances in Mesos with dynamically
 therefore have an on-box StatsD instance to report to. Therefore this little program can be started with a dynamic
 port and report metrics out to DogStatsD!
 
+# Docker
+A public docker image is available on [docker hub](https://hub.docker.com/r/keen/redis-statsd/).
+
 # Notes
 
 ## A Word On Counters
@@ -43,4 +46,4 @@ optional arguments:
   --statsd-port STATSD_PORT
                         The port of the Redis port to connect to
   --no-tags             Disable tags for use with DogStatsD
-```
+```