Ability to pass flags to child process

[timfallmk]

Hi Guys! I've been poking around looking for a good way to daemonize a function within our app I came across this. Most of the suggestions come down to "don't", and the existing libraries, namely https://github.com/sevlyar/go-daemon are pretty hacky and don't function properly.

This does seem to be missing one key feature that would make it perfect for us though. I need to be able to pass arguments and flags to the child process, rather than just run a new copy. I'm happy to try and add this feature if needed.