[DUP] Added the ability to use normal arguments

Manually created pull request to my open repo so that I could add this without firing up git.
The orginal pull request was made by Colton Wolkins ( @Frostyfrog ) here: https://github.com/rubenv/node-systemd/pull/10
- Josh ( @nevercast )

-------- ORIGINAL --------
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>