Warn if an application lacks a Store property

Attempts to use model class related methods that alias
to the store currently throw
`TypeError: Cannot read property 'find' of undefined`

This commit improves the message and offers a suggested
solution.
Fixed trailing commas which breaks IE7.
Update Readme unit test section
Introduce a custom `keyForHasMany()` for `DS.RESTSerializer`.

This method returns the singularized key appended with `_ids`. It uses the same plurals hash on the serializer to determine singular versions of keys.

Fixes #710
Merge pull request #713 from bradfol/readme-tests

Update Readme Unit Test section
Merge pull request #727 from dgeb/rest-adapter-has-many-ids

Introduce a custom `keyForHasMany()` for `DS.RESTSerializer`.
Add missing suspendRelationshipsObservers for belongsTo in ChangeRemove
Merge pull request #715 from sandstrom/relationship-change-remove-belongs-to-loop

Add missing `suspendRelationshipsObservers` for belongsTo in DS.RelationshipChangeRemove
Warn, don't fail, when there are no fixtures
Fail rather than returning all fixtures when queryFixtures is not implemented
Use Ember.run.later instead of setTimeout in FixtureAdapter
Be asynchronous (though deterministic) when simulateRemoteResponse is false

It's not clear that there is really a use case for synchronous responses
in FixtureAdapter. Asynchronous responses on the other hand are much
preferable for realistic testing.
Merge pull request #744 from CrowdStrike/fixture-adapter

Fixture adapter
Merge pull request #700 from airportyh/fix_trailing_commas_ie7

Fixed trailing commas which breaks IE7.
Merge pull request #707 from CrowdStrike/missing-fixtures

Warn, don't fail, when there are no fixtures
Merge pull request #706 from CrowdStrike/query-fixtures

Fail rather than returning all fixtures when queryFixtures is not implemented
Merge pull request #689 from trek/improve-error-message-for-missing-store

Warn if an application lacks a Store property