Add backwards compatibility for Upstart

[conradev]

Add separate templates for older versions of Upstart (that do not have setuid/setgid and env)

[Azrael808]

Hey @conradev IDK if you ever got around to implementing this somewhere, but I've made a PR to fix the Upstart stuff for CentOS 6: #14

Please let me know if there are any amendments you'd like me to make.

[mburns]

I think generalizing the init system that is supported is a great idea. Given the Upstart is deprecated in large part, I don't know that we should focus on supporting those versions, outside of modern Ubuntu and CentOS.

Thanks @Azrael808 for your CentOS fix! 😄