Updates to Wal-listner

[sidharthramesh]

Fork - https://github.com/LucasRoesler/wal-listener/tree/feature-openfaas-hacks Changes to be made:

• Wait for postgres - https://github.com/ufoscout/docker-compose-wait
• Better different topic for each table with prefix : "prefix.topic." - preferably set via environment variables.

[sidharthramesh]

Pushed as part of https://github.com/medblocks/wal-listener