Ports

Hi guys. I lost some time yesterday figuring out why starting `guard-jasmine` on port 6666 doesn't work and thought it would be nice to add a note to `README` about it. Also in these cases an exception is being thrown and Jasmine Server is not stopped. I have added an `ensure` block that will always stop the server.

I also would like to ask if you know how to work around it in a more reliable way? Ideally we'd like to catch the error thrown from PhantomJS and communicate it to the user, but no error is being thrown - `fail` status is returned, but none of the failing callbacks are being called.