Add record unloading support

Add unloadRecord() method to record instance aand to the store.
We also unlaod records when they are deleted and saved.
Clear test timer on observer execution

Fixes the build when run within the browser.
Number object doesn't have a search method
- If your REST service returns a Date as a number, the deserialization
  fails because the transform fromData tries to use search on a number
Added test for tranforming a timestamp (number) into a Date
Allow belongsTo to specify inverse
Handle some create and update errors in the REST adapter.

* 422 Unprocessable Entity

  Transitions the record to the invalid state. Assumes
  the server has responded with `{errors: {...}}` and
  sets them on the record.

* All other status codes

  Transitions the record to the error state.

This is limited to only single, non-bulk creates/updates.
Merge pull request #483 from iperdomo/master

Fixes issue when a date is serialized as a Unix timestamp
Merge pull request #482 from elliterate/fixture-adapter-test-fix

Clear test timer on observer execution
Merge pull request #476 from mhelabs/server_error_handling

Handle some create and update errors in the REST adapter.
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