Improve /rubber-duck interview

[stevepolitodesign]

I thought this was awkward:

/rails-consultant:rubber-duck if we disable a default filter, it should not appear as a category. For example, if I did this:

TopSecret.configure do |config|
  config.email_filter = nil
end

Then calling `#categories` should omit `:email`

And the skill responded with

Tell me about it. What's going on?

[stevepolitodesign]

Addressed in #24