Release v4.0.1

Fixed

• DeferredFieldSpec (the lazy stand-in introduced in 4.0.0 for belongs_to
  foreign-key field specs) now transparently delegates the FieldSpec read
  API (.options, .type, .limit, .null, etc.) to its memoized resolved
  spec. Application code that reads Model.field_specs[name].options at
  runtime would raise NoMethodError: undefined method 'options' for an instance of DeclareSchema::Model::DeferredFieldSpec.