Changes `App.PostSerializer = DS.Serializer.extend(..)` to `App.PostSerializer = DS.JSONSerializer.extend(..)`.
Updated to `DS.RESTSerializer`.
Changes all mentions of `DS.JSONSerializer` to `DS.RESTSerializer`.
Merge pull request #1172 from KasperTidemann/master

Changes `App.PostSerializer = DS.Serializer.extend(..)` to `App.PostSeri...