Bug 1079578 - [Autolander] Persist "subscribed" bugs in azure table storage

.https://bugzilla.mozilla.org/show_bug.cgi?id=1079578
So this is going to cause big scaling problems... PartitionKey is what azure table storage uses to scale across nodes. Ideally this is going to be something you know the value of but is not ordered. (You could try hashing the bug number?)