Check against email (author) array to ensure this 'pusher' is allowed

In hook.php it says:

    // Adding `prod` branch to deploy for `production` to path `/var/www/testhook/prod` limiting to only `user@gmail.com`
    $hook->addBranch('prod', 'production', '/var/www/prod', array('user@gmail.com'));

However, there isn't any code in `class.GitHubHook.php` or `hook.php` to prevent a different user who pushes to the branch to update the code on the server that has the deploy hook. I've added code which enables a remote pull if:

  * the author array is empty **OR**
  * the pusher email is in the author array