Support for https servers

Fairly trivial change set.

I generated the test key and cert by following Node TLS docs (http://nodejs.org/api/tls.html#tls_tls_ssl), and added a simple test to ensure the correct protocol is being detected.
I had wondered about this. If we're to ditch the string concat in this instance I'd be interested in reworking this completely to expose the URL via an api. Something like:

```js
servertest(server).address();
// 'http://localhost:8080/'
```

I've a few cases where this would come in handy. Thoughts?