Add record unloading support

Add unloadRecord() method to record instance aand to the store.
We also unlaod records when they are deleted and saved.
Merge pull request #200 from tchak/unload-record

unloadRecord()
clientIdToHash -> clientIdToData
Merge pull request #484 from tchak/fix-unloading

clientIdToHash -> clientIdToData
Fix relationship change when restoring old value

This addresses two issues:

* Restoring the child to the original value

  This is necessary when the restoration is triggered by a change on
  the parent.

* Removing the dirty factor from `lastParent` (the penultimate parent)

  Aside from actually removing the dirty factor in the `destroy()`, this
  also requires suspending `lastParent`'s association observers when
  removing the child from it.

  If that didn't happen, `lastParent`'s `arrayContentWillChange()` would
  set `newParent` to null and trigger another sync of the relationship
  change, which would then cause `lastParent` to get set to null before
  the change's `destroy()` can be called.
Merge pull request #485 from mhelabs/relationship_change_restore_fix

Fix relationship change when restoring old value
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.
Implements adapter dirtiness hooks

This commit adds the ability for the adapter to
specify which records should be marked dirty when
changes occur, such as when an attribute or
relationship changes.

If you are using the REST adapter, it should
not introduce any breaking changes.

For more information about the rationale
behind this change, please see
BREAKING_CHANGES.md, revision 9.
Resolve merge conflicts
Fix REST adapter error handler invocation

Addresses #486.
Add inline docs to injection code
Adds unit test for DS.Model associations property
Add inline docs for association introspection
Normalize integration test names
Merge pull request #489 from elliterate/rest_error_handler_fix

Fix REST adapter error handler invocation
Update to use Ember.lookup instead of window
Fix breaking changes API typo
Remove JSON semantics from DS.Serializer
WIP on embedded records
Add doc for store.recordIsLoaded

References issue #500