Add created_by field for contribution.

subathon/data.py

@@ -37,7 +37,7 @@ class SubathonContribution(RowModel):
     profileid = Integer()
     score = Integer()
     event_id = Integer()
-    # TODO: Should add a created timestamp here, since not all contributions have event ids
+    created_at = Timestamp()
 
 class SubathonGoal(RowModel):
     _tablename_ = 'subathon_goals'