(lame) added initialize rails to model_spec_helper to remove warning

I'm most likely doing something wrong, but I kept getting this warning:

```
uninitialized constant <Model Name>::Rails (NameError)
```

when requiring model specs from ``model_spec_helper``. The tests would still run, but requiring this got rid of the warning. But then again it's initializing Rails, which is the anti-thesis of your blog. With rails 4.1  (with spring) and the ``Guardfile`` referenced in #1 it's not horrible, but I think it's far from what you had in mind.