Show built version and SHA on start-up

[alexellis]

Show built version and SHA on start-up

Expected Behaviour

Users should be able to identify versions from logs

Current Behaviour

You can inspect the Docker image

Possible Solution

See the logs of faas-netes and use the same approach

Steps to Reproduce (for bugs)

1. arkade install openfaas
2. kubectl logs -n openfaas deploy/queue-worker

Context

Better consistency and logging.

[amalkh5]

fixed by #93

[alexellis]

Thanks @amalkh5