this changes the interface to move the readiness check out of
the classifier and into the stream object. This massively
simplifies the logic connecting these pieces, as classifier is
now just a thin wrapper to elastic search.
This also adds unit testing for the stream processing through the
creation of a fake_gerrit mock class. That lets us run gerrit
event interactions in a sane way.
It also drops all the unit testing for the classifier which is now
largely useless, because all it tests is we can execute a for loop.
Change-Id: I1971c121276412e31f01eb5680b9c41fc7e442d3
7f42043155