this could also be a predicate method

```ruby
def is_active_record_4_0?
  (ActiveRecord::VERSION::MINOR == 0) && (ActiveRecord::VERSION::MAJOR == 4)
end
```

Then we'd just have:

```ruby
if is_active_record_4_0?
  active_record_4_0_association_relation_delegate_class(model_class)
else
  active_record_4_1_association_relation_delegate_class(model_class)
end
```