Ensured -t flag was passed to mini script execution of the Hello World daemon

The tutorial assumes detaching after attaching is possible, such that you can run `sudo docker ps` and see that the container is still running.  

Prior to this edit, the tutorial instructed the reader to press Control-C to detach.  As of Docker 0.6.5, this actually terminates the backing process.  Running `sudo docker ps` next in the tutorial showed nothing and was confusing - it 'broke' the remainder of the tutorial.

Adding `-t`, the reader can exit via ctl-p ctl-q and the remainder of the tutorial is possible.