Add health check endpoint

Author: callmekatootie

README.md

@@ -35,6 +35,8 @@ The following parameters can be set in config files or in env variables:
 - ELASTICSEARCH_INDEX: the Elasticsearch index to store Kafka messages data, default value is 'submission-index'
 - ELASTICSEARCH_INDEX_TYPE: the Elasticsearch index type name, default value is 'submission'
 
+Also note that there is a `/health` endpoint that checks for the health of the app. This sets up an expressjs server and listens on the environment variable `PORT`. It's not part of the configuration file and needs to be passed as an environment variable
+
 ## Local Kafka setup
 
 - `http://kafka.apache.org/quickstart` contains details to setup and manage Kafka server,