Fix authentication

According to Guzzle Docs (and to make it work for me), I needed to adjust the authentication to match this: http://guzzle.readthedocs.org/en/guzzle4/clients.html
Allow overriding guzzle options in Transport object

This then allows me to override like this:

```php
        $connection = new Transport($url, $params['username'], $params['password'], [
            'defaults'=> array(
                'headers' => array(
                    'Accept' => 'application/json',
                ),
                'auth' => [$params['username'], $params['password']]
            )
        ]);
        $this->targetprocess = new Client($connection);
```

Overriding the 'auth' config option, so it works for me (without breaking your existing version)! :-)
Change auth to use Guzzle config option by default again
Update README to show example of alternate config
Update Guzzle config override example

To use full namespace
Merge pull request #2 from manavo/patch-2

Fix authentication