Support passing a custom ArraySerializer for has_many associations

Thanks @phoet

Closes #316
Split root construction and serialization logic
has_one returns arrays with roots pluralized
Improve build_json_serializer readability a bit
Move responsibility of setting a serializer class and building a serializer for an association to the association class
Merge branch 'has_one_arrays_pluralized'
Make Associations in root work with ArraySerializer

Closes #414
Make ArraySerializer reuse Serializer embedded_in_root_associations code
Merge branch 'association_in_root_array_serializer'
Embed objects should return singular and not wrap in array

Closes #437
Add note about master on README
embedded_in_root_associations is always defined
Make DefaultSerializer include AM::Serializable so embedded_in_root_associations is always defined also there
Make tests pass on jruby
Merge pull request #440 from strzalek/jruby-tests

Make tests pass on jruby
Change hardcoded class in favor of using provided serializer class in AR integration tests
Merge pull request #441 from jmbejar/ar_integration_test_harcoded_class_fix

Change hardcoded class in favor of using provided serializer class in AR integration tests
Don't treat has_one associations embed objects as an array

Closes #442

Thanks @arrtchiu for reporing and giving a test case
Pass scope through to associations via @lastobelus

Closes #433
Fixed Rails 4 Controller Scaffold Generator.