Merge pull request dockersamples#60 from docker/duplicate_key

note about one vote per client

Author: Mano Marks

README.md

@@ -23,3 +23,8 @@ Architecture
 * A Postgres database backed by a Docker volume
 * A Node.js webapp which shows the results of the voting in real time
 
+
+Note
+----
+
+The voting application only accepts one vote per client. It does not register votes if a vote has already been submitted from a client.