added hooks and plugins files missing

tests/test_events.py

@@ -0,0 +1,7 @@
+import app.events as events
+
+def test_event_names_exist():
+    assert hasattr(events, 'ON_USER_CREATED')
+    assert hasattr(events, 'ON_SUBMISSION_SAVED')
+    assert hasattr(events, 'ON_PLANT_TRANSFERRED')
+    assert hasattr(events, 'ON_GROWLOG_UPDATED')