Fixed about_inheritance.rb to pass tests

Learned about/that:
* subclasses have the parent as an ancestor,
* all classes ultimately inherit from object,
* subclasses inherit behavior from parent class,
* subclasses can also add new behavior.

[#65851788]
Fixed about_inheritance.rb to pass tests

Learned that:
* subclasses can modify existing behavior,
* subclasses can invoke parent behavior via super,
* super does not work cross method.

[#65851788]
Merge pull request #23 from mkreyman/65851788_about_inheritance_master

about inheritance master

[Delivers #65851788]