Add ability to use hanami-entities as a base object

[davydovanton]

Something like this:

module Api::Serializers
  module Controller
    class Show < Hanami::Serializer::Base
      entity User
    end
  end
end

[frostmark]

@davydovanton i can take it

[frostmark]

@davydovanton Can you describe in more detail this feature?

[davydovanton]

hey, I'm thinking about change this repo to other version that's why let's hold this issue before 0.2 release 👍