Fixes def my_global_methods -- def test_calling_with_default_values.

I learned:

* Global methods can be used with or without parentheses, though some-
times parentheses are needed.

* Global methods must have appropriate number of arguments.

* If dafaults values are given, they are called whenever methods don't 
specify for that value.

[#65851850]
Fixes def method_with_var_args --  def 
test_calling_methods_in_same_class_with_explicit_receiver

I learned:

* Methods with or without explicit returns will return
:return_value over :a_non_return_value.

* Calling methods in the same class returns the same result as calling those
in the same class with an explic receiver (ie self.)


[#65851850]
Fixes def test_calling_private_methods_in_other_objects

* I learned that trying to call a private method on something non-private
will give NoMethodError.

[#65851850]
Fixes def my private method:

I found the following on stack overflow, it was the only thing that worked
for def test_calling_private_methods_with_an_explicit_receiver:

assert_match /private method `my_private_method' called 
for \#\<AboutMethods:.*/

* I learned a regex was required because object ID for the class 
AboutMethods will change every time it's called, so a reg ex is better to use.

[#65851850]
Fixes def test_calling_private_methods_in_other_objects

* I learned that trying to call a private method on something non-private
will give NoMethodError.

[#65851850]