Add email address

By using the right scope we have access to user's email:

```php
// Using LinkedIn strategy for Opauth
Configure::write('Opauth.Strategy.LinkedIn', array(
	'api_key' => 'XXXX',
	'secret_key' => 'XXXX',
	'scope' => 'r_basicprofile r_emailaddress',
	'profile_fields' => array('id', 'first-name', 'last-name', 'formatted-name', 'headline', 'picture-url', 'summary', 'location', 'public-profile-url', 'site-standard-profile-request', 'email-address')
));
```