Add option to disable spinner in `--watch`.

I'm unable to use [node-foreman](/NodeFly/node-foreman) with `--watch` because of the spinner animation -

Screenshot with spinner:
![Screen Shot 2013-04-11 at 8 51 15 PM](https://f.cloud.github.com/assets/217126/368300/7b74a716-a2bc-11e2-97aa-13ec54b2040e.png)

and without:
![Screen Shot 2013-04-11 at 8 53 59 PM](https://f.cloud.github.com/assets/217126/368304/81dc84ac-a2bc-11e2-88b1-1e23fcf60215.png)

Let me know if something needs to be changed.