Flock: added Advisory subscription support

see https://github.com/GigaOM/legacy-pro/issues/4525
hmmm those sound like two different comment blocks. are you scrolling horizontally? in the context of the whole file here: https://github.com/GigaOM/go-subscriptions/blob/flock/components/class-go-subscriptions.php#L406 i see

![screen shot 2014-12-04 at 2 31 40 pm](https://cloud.githubusercontent.com/assets/3730514/5307490/6420e954-7bc2-11e4-8d48-de9c3f67f53d.png)