Patch Earned Achievements more generally.

server/commons/mapping.coffee

@@ -66,4 +66,5 @@ module.exports.modules = modules = # by collection name
   'users': 'User'
 
 mongoose.modelNameByCollection = (collection) ->
+  return require('../models/LevelSession') if collection is 'level.session'
   mongoose.model modules[collection] if collection of modules

server/handlers/earned_achievement_handler.coffee

@@ -51,9 +51,8 @@ class EarnedAchievementHandler extends Handler
     collection = req.body.collection
     if collection isnt 'level.sessions'
       return @sendBadInputError(res, 'Only doing level session achievements for now.')
-      #model = mongoose.modelNameByCollection(collection)
-    else
-      model = LevelSession
+
+    model = mongoose.modelNameByCollection(collection)
 
     async.parallel({
       achievement: (callback) ->