v0.3.2

This release fixes a synchronisation delay issue. The pending message job blocked
while waiting for the last pending messages in the queue to be processed. This caused
a delay of several hours until the job could loop again on the pending messages collection
and start processing new pending messages. We removed the blocking synchronisation point
and now let the job pick up new pending messages while ignoring the ones that are already
being processed.

How to upgrade: https://pyaleph.readthedocs.io/en/latest/guides/upgrade.html