Add debian upstart script.

For those that want to use an upstart-based init I've created on that I'm using locally. Note that there is an assumption that the user is "chronos".  I can't take credit for the logger stuff, as that was jacked from both the mesos-init-wrapper and [this answer on StackOverflow](http://serverfault.com/questions/114052/logging-a-daemons-output-with-upstart).