Fix error: "alize does not work with default scope"

[nazarok]

This pull request added configuration options to disable default_scope.

Mongoid::Alize.setup do |config|
config.unscoped = true
end

[joshed-io]

Thanks @web-patriot!

I pulled down the PR and I'm getting some failing tests when I run bundle exec rake spec. Here's an example:

  42) Mongoid::Alize without specifying fields for non-polymorphic should denormalize all non-internal fields
     Failure/Error: @person.save!
     NoMethodError:
       undefined method `scoped' for #<Head:0x007ffc0d2113d8>
     # ./lib/mongoid/alize/to_callback.rb:22:in `_denormalize_to_head'
     # (eval):1:in `block in make_lambda'
     # ./spec/mongoid_alize_spec.rb:238:in `block (4 levels) in <top (required)>'

Can you check and see if you're getting any failures?