* Fetch conversation messages with BS4 and regex as fallback.

* Fetch conversation messages with BS4 and regex as fallback.
-- To fetch messages call `update_messages` on a `models.Conversation` object.
-- You may now do `iter`, `len` and `getitem` with a `models.Conversation` object to get messages or to get the message count.
-- Call `messages` in a `models.Conversation` object to receive a list with messages (dict)
* BS4 for Notification model and kept regex as fallback.
* Did a trick in Notifications who() function to get a unique list without duplicates.