Wrong Docker images name in README.md

[FTWH]

faas-cli deploy --name receive-message --image openfaas/receive-message:latest --fprocess='./handler' --annotation topic="nats-test"

openfaas/receive-message:latest does not exist. It perhaps renamed with openfaas/nats-receive-message:latest

[alexellis]

@LucasRoesler PTAL?

[a5r0n]

@alexellis
probably its with nats- - openfaas/nats-receive-message

EDIT:
now i see #21