Add serialization_options

Prior to 0.9, @options was used to see the options passed to to_json. For some reason, with 0.9 the options were no longer passed and were entirely inaccessible within a Serializer.

This restores the access by placing it in an attribute named serializer_options.
Fix serialization_options for array serialization
Merge branch 'serializer-options' into 0-9-stable