Testing updates

[kilgore5]

• small refactor to delay including InstanceMethods until unique_id is called on the class
• this way we can make a custom matcher to test (in part) the inclusion of the instance methods on the class as partial evidence that the class is using unique_id
• note: currently depends slightly on Refactor constant usage #2 but those updates can be easily taken out

custom matcher references

• https://github.com/rspec/rspec-expectations/blob/master/Should.md
• https://medium.com/@igor_marques/writing-custom-matchers-15bd3d866079
• http://rspec.info/documentation/3.7/rspec-expectations/RSpec/Matchers.html
• https://relishapp.com/rspec/rspec-expectations/v/3-7/docs/custom-matchers/define-a-custom-matcher
• https://robots.thoughtbot.com/shoulda-matchers