Merging in environment variables over top of properties

New feature request I've noticed. Instead of a defaults file with safe values for CI/CD systems, I would much more often like to be able to inject secrets such as API Keys through environment variables.

Parsing the environment for prefixed environment variables (something like SECRETS_NAME_OF_SECRET) to merge over top of the defaults and merging all of the mappings sensibly before injecting would be insanely helpful for CI/CD systems that also handle deployment to beta testing and the like.