Fixed about_classes.rb to pass tests

Learned about:
* instances of classes created with new,
* assignment of instance variables,
* asking for instance variables values with #instance_variable_get,
* use of #instance_eval.

[#65851782]
Fixed about_classes.rb to pass tests

Learned about/that:
* creating accessor methods to return instance variables,
* attr reader will automatically define an accessor,
* attr accessor will automatically define both read and write accessors,
* initialize provides initial values for instance variables,
* args to new must match initialize.

[#65851782]
Fixed about_classes.rb to pass tests

Learned about/that:
* inside a method self refers to the containing object,
* uses of #to_s in string interpolation,
* inspect provides a more complete string version,
* all objects support to_s and inspect.

[#65851782]
Merge pull request #19 from mkreyman/65851782_about_classes_master

about classes master

[Delivers #65851782]