--------------------------
- Added bouncing support: The new utility view
``dancing.utils/handle_bounce`` takes a list of addresses and
marks subscriptions as pending when it receives more than two bounce
notifications. This has the effect that no more messages are sent
to that subscription, while the subscription is still present in the
database. [nouri]
- Added caching to composer rendering. Caching is done based on
``_vars`` and collected items. Notice that ``composer._vars`` has
been split into two; ``_vars`` and ``_subscription_vars``. The
latter containing variables that are likely to be unique to the
subscription, and the former those that are likely shared across
multiple subscriptions.
Rendering is now broken into two step:
1) Rendering the ``composer-html`` template and compacting the
resulting html with StoneAgeHTML. ``_vars`` and collected items
is available in the template. This step is cached on ``_vars``
and items.
2) ``string.Template`` variable replacement on the html of variables
in ``_subscription_vars``. In the default implementation only
the subscribers secret in the subscription management urls is
replaced.
[tmog]