Enable including a LightService::Organizer

I remember you suggesting that it would be awesome if we could `include LightService::Organizer` instead of `extend LightService::Organizer`. Here's that needed changes for that. :tada: 

extra goodie: extending `LightService::Organizer` still works, though explicitly removed from the examples. Just revert the `organizer_spec.rb` to use `extend` instead of `include` to check. :+1: