Update loader_query.rb

stringify association key name (so that the associations can be also specified as symbols)

Author: tomasc

lib/torque/postgresql/associations/preloader/loader_query.rb

@@ -6,7 +6,7 @@ module Associations
       module Preloader
         module LoaderQuery
           def foreign_column
-            @foreign_column ||= scope.columns_hash[association_key_name]
+            @foreign_column ||= scope.columns_hash[association_key_name.to_s]
           end
 
           def load_records_for_keys(keys, &block)