Added the ability to use normal arguments

Wonderful node module, I only found one problem with it on my end
though. When I wanted to add a callback like normal, I couldn't do so
with systemd and it would just get passed back onto the old listener
object, which wasn't something that I wanted (obviously). Fixed that
along with the other operators. Judging by Node's code, this should work
and not have any negative side effects.

Signed-off-by: Colton Wolkins (Frostyfrog) <frostyfrog2@gmail.com>
Merge pull request #1 from frostyfrog/master

Added the ability to use normal arguments