Using auth details from server url in http requests

I found that the auth details from the parsed server url was not being copied into new requests with the host and port. Fixing was very easy.

Allows working with Sauce Labs using:
```
var driver = new webdriver.Builder()
    .withCapabilities(...)
    .usingServer('http://USERNAME:AUTHCODE@ondemand.saucelabs.com:80/wd/hub')
    .build();
```

I've signed the [CLA](http://goo.gl/qC50R).