One interesting thing to be doing is polling for new events on a
project. Right now, the only event is series-new-revision, so listening
to events is really just listening to series creation and update.

This is quite useful for testing infrastructures, knowing when a series
is ready to be tested so a bot can retrieve its patches and test them.

Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>