remove obsolete reference to env.ZERIGO_DNS_KEY and env.PERSONA_DEPLOY_DNS_KEY; add a way to specify default domain with env.PERSONA_DEPLOYMENT_DOMAIN
Merge pull request #3984 from jrgm/de-zerigofy-scripts-deploy

remove obsolete reference to env.ZERIGO_DNS_KEY and env.PERSONA_DEPLOY_DNS_KEY 

Nice cleanup @jrgm. Ephemeral deployments work every bit as well as before this PR. r+