Be quiet if -q is set an no errors occurred

We (@adcloud) are using [jshint](https://github.com/jshint/jshint) to check our javascript files before committing them. We want to use CoffeeLint for our coffeescript files, but we only want to see any output if an error occurred.

At the moment CoffeeLInt outputs a summary even if `-q` is given and no errors occurred. I think, `-q` should disable __every__ output unless an error occurrs.