Set custom URL on the REST adapter
Make async helper global to tests
Clean up Ember.Application integration test
Prep for moving waitingOn to adapter

This commit starts us down the path of moving the
logic for pending/waitingOn into the adapter.
Update ember
Stop segregating transaction records by type
WIP on moving relationships to adapter

This commit is a work-in-progress on our work to
separate out the semantics between dirty records
and changes to their relationships.

Highlights:

1) DS.Model#toJSON() now accepts more arguments to
change how it serializes relationships
2) WIP on adapters being more active participants
in deciding what records need to be committed
3) Changed belongsTo attributes no longer write
ids to the record's data proxy
4) Records can be moved from the loaded.saved
state to a new relationshipsInFlight state. This
means that the record has changed relationships
but not changed attributes that need to be
persisted
5) Transaction now includes records that are not
dirty but have changed relationships when calling
an adapter's `commit` method (in the `updated`
array of records)
Remove pending stuff
WIP do more stuff in the adapter

The most important change here is that filters now
materialize records.

This is necessary because the records no longer
store their backing data as a serialized hash.

The long-term perfz plan (for situations with huge
numbers of data hashes) is to integrate with
something like crossfilter to filter out unneeded
records before loading into the store.
Consolidate and update filter tests

Add new tests for computed properties and state
flags for filtering.

Note that only computed properties that depend on
attributes can be used in a filter.
Remove duplicate tests
Add serialization object
Ensure QUnit module for automated JSHint tests
Add warning for unimplemented adapter methods
Rearrange adapter file structure
Break apart materialize
Update tests to use adapter's toJSON method
Change semantics for reporting unloaded attributes

Previously, if a record was not yet loaded,
retrieving an attribute would return null. Now,
undefined is returned instead.
Continue firming up the adapter<=>record API
Encapsulate serialization and deserialization

Previously, concerns about how key names
for given hashes returned from the server were
spread across several different objects.

Now, the serialization and materialization
(converting an opaque data hash returned from
the server into meaningful results for Ember Data)
are handled by the DS.Serializer object.

Instead of jamming this responsibility into the
adapter, like so many clowns in a clown car, the
adapter is now solely responsible for deciding
which records should be committed, loading
records, and notifying the store of changes in
to record state.