refactor follows and update_nofications indexing

Based on !819 (closed)

Require tests_api!258 (merged)

tests/api_tests/hivemind/tavern/bridge_api_patterns/unread_notifications/abit.pat.json

 {
   "lastread": "2016-04-29 04:11:57",
-  "unread": 1922
+  "unread": 1894
 }