Update Readme unit test section
add fixture serializer
use adapter interface in fixture adapter
Merge pull request #716 from tchak/fixture-adapter-cleanup

Fixture adapter cleanup
Implement extractHasMany and extractBelongsTo
Merge pull request #718 from tchak/fixture-adapter-cleanup

Implement extractHasMany and extractBelongsTo on FixtureAdapter
Merge pull request #713 from bradfol/readme-tests

Update Readme Unit Test section