Does attributable work with "deep" inheritance of mix-ins?

[louismrose]

Add tests to investigate whether or not inheritance / includes of depth > 1 work well.

For example, does the the following work well? Does the same example work well when specified using modules and include?

class Person
  extend Attributable
  attributes :name, friends: []
end

class Employee < Person
  attributes :salary, officemates: []
end

class Salesperson < Employee
  attributes :bonus, quota: 100
end