Fix about_methods koan

* Basics of methods, how they respond to args
  and what they return, explicit or non-explicit

* Expected error messages for Argument Error

* While parentheses not always required, should
  use them to avoid ambiguity in expressions

[#54145651]
Fix about_methods koan

* self.my_method_in_the_same_class(3,4) (ln 105)

* in IRB returns NoMethodError: private method

* koans insists that '12' is correct answer!

[#54145651]

self.my_method_in_the_same_class(3,4)
Fix about_methods koan

* private_methods problematic 

* ln 123 requires only partial of returned error
  message, including full message throws an
  error regarding object.

[#54145651]
Merge pull request #10 from bayendor/54145651_about_methods_master

Fix about methods koan

[Delivers #54145651]