Add method to get number of queued project updates

services/document-updater/app/coffee/RedisManager.coffee

@@ -315,6 +315,9 @@ module.exports = RedisManager =
 
 		rclient.rpush projectHistoryKeys.projectHistoryOps({project_id}), jsonUpdate, callback
 
+	numQueuedProjectUpdates: (project_id, callback = (error, length) ->) ->
+		rclient.llen projectHistoryKeys.projectHistoryOps({project_id}), callback
+
 	clearUnflushedTime: (doc_id, callback = (error) ->) ->
 		rclient.del keys.unflushedTime(doc_id:doc_id), callback