Replace Hydra::Presenter#to_model delegation with self

[no-reply]

Beginning in v3.5.1, SimpleForm::FormBuilder calls #to_model (via
ActionView's #convert_to_model) in its initializer. This prevents
Hydra::Presenter inheritors from being used correctly when sent to the
form. Replacing the delegated method with one that returns self restores the
correct behavior to SimpleForm::FormBuilder and related view helpers.

Client code can still access the model by calling the #model accessor.

Fixes #139.

[no-reply]

A hyrax build running this code is at https://travis-ci.org/samvera/hyrax/jobs/349501904

[jrochkind]

This seems to be in line with what ActiveModel#to_model expects

http://api.rubyonrails.org/classes/ActiveModel/Conversion.html#method-i-to_model

If your object is already designed to implement all of the Active Model you can use the default :to_model implementation, which simply returns self.… If your model does not act like an Active Model object, then you should define :to_model yourself returning a proxy object that wraps your object with Active Model compliant methods.

That is, if it's already ActiveModel-compliant, just return self, only return something else if you want something wanting an ActiveModel to use that, which is why simple_form was using that.

[jrgriffiniii]

Thank you @no-reply for linking to the related Hyrax test