Add transform per attribute based serializer.

* Add TransformInterface.
* Add serializer test case.
Add serializer container.

* Add SerializerContainer test.
Add transform classes.

* Add boolean, integer, float, string, and date transforms.
* Add test cases.
Remove old serialization and transform classes.

* Remove previous transform classes.
* Remove deprecated class SerializerContext.
* Remove ModelSerializer (superseded by Serializer).
* Remove TypedSerializer (superseded by SerializerContainer).
Refactor ModelPool as MemoryResponseWriter.

* Implement ResponseWriterInterface.
* Apply PSR-2 code style.
Remove deprecated interfaces.

* Remove ModelProxy since adapters now return and can use underlying
objects directly.
* Remove ModelIterator; similarly model collections do not need to be
wrapped.
Configure autoloader to map namespaces instead of classes.
Apply PSR-2 format and comments to AttributeType code.
Add attribute class which uses properties, accessors, or callables.

* Add test case.
Add adapter base class.
Add Yii test base class that manages framework loading.
Remove old Yii test classes and configuration file.
Add ActiveRecord adapter container and factory.

* Add test case.
Refactor ActiveAdapter.

* Update to match new adapter interface.
* Add relations attribute classes.
* Add new mock based test case.
* Apply PSR-2 style.
* Remove model proxy and iterator classes.
Add class to represent HTTP responses with JSON API format.

* Add test case.
Add utility class to handle JSON API HTTP requests.

* Add test case.