Provide the same functionality as the [`RESTSerializer`'s `pushPayload`](https://github.com/emberjs/data/blob/master/packages/ember-data/lib/serializers/rest_serializer.js#L508) but specific to our serializer/adapter.

This allows a single record or an array of records to be manually pushed into the store, such as when pre-loading records from the server.

````
var json = {"id": 10, "description": "django"};
// load the object into the Ember data store
var store = App.__container__.lookup("store:main");
store.serializerFor('tag').pushSinglePayload(store, 'tag', json);
````
Merge pull request #41 from craigteegarden/ember1.0-add-pushPayload-capabilities

Ember1.0 add push payload capabilities
added failing integration test for issue #40