add assign_attributes method because it's used by Devise
Fold in rlivsey's multi_parameter attributes for AR parity
Use ActiveModel's mass assignment protection for better parity with AR.
Merge protected and accessible
Make multiparam attributes respect the plugin architecture. Fix attributes= and assign_attributes to match AR call semantics.
Change attr_protected semantics to match the Rails environment it's loaded in

Remove unnecessary require

Minor performance improvements

Fix sanitization call semantics for Rails 3.0.x

Remove explicit inclusion of MP attrs plugin on spec model
Make Rails 4 the build default for this Gemfile. Make travis build explicit gemfiles
When under Rails 4, warn about scopes that don't pass a lambda or method name. Preserve backwards compatibility with Rails 3.
Streamline scope deprecation warnings a bit