* API change: :meth:`~tidings.events.Event._mails()` now receives,
in each user/watch tuple, a list of :class:`~tidings.models.Watch`
objects rather than just a single one. This enables you to list all
relevant watches in your emails or to make decisions from an
:class:`~tidings.events.EventUnion`'s ``_mails()`` method based on
what kind of events the user was subscribed to.
* Expose a few attribute docs to Sphinx.