Make reading state work for non-AR models?

I couldn't get this to work in a MongoMapper model and removing the constraint on the AR descendent fixes it for me in my app.

NOW, I can't get some of the tests to pass and can't figure out why. Any ideas?
Why are we using "ActiveModel::Dirty" here specifically?
I assume because 

```Ruby
klazz.included_modules.include?(ActiveModel)
```

would return false? How about making this clearer with a comment?