changing the shutdown log level to debug

It seemed weird to me that when I would have a grunt watch and would close it using ctrl+c, a log of the cloudfront process shutting down would come up, even if the task was never actually ran.  At that point, I don't think the process is even alive (an conditional check might be more appropriate) and I simply wanted to remove the log to not confuse any other developers.
Merge pull request #8 from mboudreau/patch-1

changing the shutdown log level to debug