DS.FixtureAdapter.findQuery takes type

Pass type into findQuery. This allows you to do custom query logic based
on what kind of fixtures are requested. Now you can switch your query
logic if Todo or Message is queried. This logic would normally be done
on the server, but you can implement it here for development purposes.
Fix breaking changes API typo
Remove JSON semantics from DS.Serializer
WIP on embedded records
Add doc for store.recordIsLoaded

References issue #500
cleanup load() & loadMany() for DS.Store
added callChangeEvents
relationships now indexed based on parent, child, parentKey, childKey
made keys for relationship changes be childKey+parentKey
changed relationship to be simple two sided, only 9 failing tests
removal from old manyArray when added to a new one works
added relationship pairs function and made coalescing work
deleting old code
deleting more old code
Bump ember to master
Improve error message shown when DS.StateManager is sent an action that its current state doesn't handle.

This improvement relies on functionality in ember.js 0da99312438204c or newer, though it should be a no-op
for older versions.
Merge pull request #509 from lukemelia/statemanager-error-improvements

Statemanager error improvements
Update Ember and update a test to use createWithMixins.
Fix typo
Define Ember's new `toStringExtension` on `DS.Model` to include the record's `id` property in `toString` output