_replace_refs should use mapping and sequence type information from inbound object

[bdanofsky]

I would like to defer some steps, e.g. deserialization of a complex object, until object access time.
This could be accomplished by setting json.load(*, cls=) and returning a collection that defers the object deserialization until a later point.
Unfortunately _replace_refs assumes all mapping types are Dicts and thus the type of the inbound Mapping object is lost.
This could be easily overcome by changing the building of the mapping
obj.class(**{.....})
this would preserve the inbound type that comes from json.load.
The same could be applied to Sequence types.

Obviously this does not apply to the replacement of the referent.