reading values via environment variables in bash

[8de2fdb0]

Reading nested environment variables is kind of impossible when using this library.

Env variables like:
APP.NESTED_CONFIG.VALUE

Don't really work in Bash, the workaround is to use a double underscore for separators __, I guess parsing would have been a bit harder if _ would be supported in that case. But from a usability perspective this is a real foodgun.

[softdevca]

In fact, dots in environment variables aren't POSIX compliant. See https://stackoverflow.com/questions/2821043/allowed-characters-in-linux-environment-variable-names/2821201#2821201