Fix serialization issues by adding json converters

deserializing the domain objects broke due to the fact that they now had
interfaces as properties and json.net no longer knew how to deserialize
them.  To fix I've added a couple Jsoncoverters to deserialize the
interfaces to the concrete types.
Add Json.Net as dependency
Missed an attribute on the user object
Merge pull request #43 from Skookum/FixSerializationViaJsonDotNet

Fix serialization issues by adding json converters