Ensure PersistentStates::Object tracks changes.

Make the generated setter method actually set the changed value.
Ensure the changes output lists the changed attribute, with both
before and after values. e.g.

    state.changes #=> { 'attribute_name' => ['old_value', 'new_value'] ... }
Merge pull request #20 from garrow/refinement/track_attribute_changed_values

Ensure PersistentStates::Object tracks changes.
Fixed blah_attributes when blah attribute is not in the params
More resilient blah_attributes handling
bugfix: _destroy should ignore when not persisted.
Slightly tweaked the if statement
Fixed Order criteria
Fixed Criteria criteria ordering
Performance optimisations (more to follow)

- Refactored the way Datamappify walks attributes to allow query optimisations.
- Optimised ActiveRecord queries for entities.
File loading fixes
Fixed ambiguous columns in order criteria
ActiveRecord structured_criteria fix for match
Case insensitive matches for postgres
Updated Virtus
Use the new Equalizer gem from Virtus
Corrected gemspec's requirement for Virtus
Release 0.70.0.beta1
Update virtus and use Virtus::Attribute#rename
Merge pull request #25 from solnic/simplify-attribute-cloning

Update virtus and use Virtus::Attribute#rename
Updated gemspec