Autostart in OS X Yosemite

After upgrading to Yosemite, I found out that spoof-mac autostart was not working.
This happens because [Apple deprecated StartupItems](https://developer.apple.com/library/mac/documentation/MacOSX/Conceptual/BPSystemStartup/Chapters/StartupItems.html).

As a consequence, I tried to fix autostart the way Apple wants, by using launchd.
I'm not an expert though, so if you find anything ugly, or wrong, feel free to change it.

And, eventually, on my system the update to version 2.0 produces a script called spoof-mac.py. So I updated the Readme consequently.