Fix about_keyword_arguments koan

* .class == Array

* defaults specified as default1: "foo"

* exceptions are for a missing non default
  keyword only, others are passed to the 
  method by default.

[#54145655]
Merge pull request #11 from bayendor/54145655_about_keyword_arguments_master

Fix about_keyword_arguments koan

[Delivers #54145655]