[Diffferences]
+ Added attribute methods.

[Reasons]
+ To clear attribute of sample.
[Diffferences]
+ Added attribute methods suffix.

[Reasons]
+ To confirm the presence of attribute of sample.
[Diffferences]
+ Added the assertion of human and singular method.

[Reasons]
+ To confirm ActiveModel::Name behavior.
[Diffferences]
+ Extended ActiveModel::Translation.

[Reasons]
+ To confirm whether model_name is translated.
[Diffferences]
+ included ActiveModel::Validations.

[Reasons]
+ Our model can respond to errors and valid? methods.
[Diffferences]
+ Added persisted? method.

[Reasons]
+ To pass the test.
[Diffferences]
+ Added deliver method.

[Reasons]
+ To delivers an email with attributes.
[Diffferences]
+ Added integration test.

[Reasons]
+ To check whether mail_form gem work well in rails app.
[Diffferences]
+ Added customized validator.

[Reasons]
+ For :nickname attribute.