Issues with localStorage when empty and when creatingRecords

Fixed some issues when creating records and fetching all records when the model isn't added to localStorage already. The Ember.RSVP.resolve() seems to be throwing an error when passing it a given record:

Assertion failed: You must use Ember.set() to access this property (of <record>)

Works fine when it's not passed the record, so not sure why it was done?

Updated _namespaceForType so it handles not having defined a given model, so it doesn't return undefined but rather an object with a records attribute as expected by Ember.

We might not even need the storage check, but rather keep it as a namespace check, but I wasn't able to find any cases where this is not working, so I stuck with it.