Support client-side authentication

Although the lib is strictly server-side, passing the access_token to the client might be a necessity in certain cases. 

This is usually done by adding the access_token to the URL as a hash, ex:

```
http://domain.name/access_token#WDEJK34RHJ7KEJNWKPSNK
```

This should the the final redirection after authentication and enabled through an option in the configuration. 
