Code that demonstrates unexpected behavior with regards to completedChangesCount of replicator observer.
Merge branch 'replicator_observer_issue' of github.com:couchbase/couchbase-lite-ios
Don’t set replication progress to 0/0 when stopping

Instead the progress should remain the way it was.
Also, improved Traun’s great new test for verifying that progress counts make sense.
Fixes #274