XML and JSON now works.
a Representer now only needs a format and computes serialize_method etc itself.
adding tests.
add test for Hash and XML where we use :as and :extend. in XML, this currently doesn't work!
the JSONScalarBinding internally now uses the ObjectRepresenter which decorates the scalar with a ScalarDecorator which itself just returns the scalar on #to_hash/#from_hash.
this is awesome since we don't have to treat scalars and objects differently but just as objects.
don't use ScalarRepresenter anymore, use ObjectRepresenter with decorator: FormatScalarDecorator which makes the Representer architecture simpler as we don't need one for scalars but treat them as objects.
reorganizing. Binding#write now wraps and calls serialize. same for #read. a CollectionBinding now uses an instance of ObjectBinding for representing.