Fixed normalizePayload, extractMeta & extractLinks for json-api ...

...url shorthand style.

The current versions (Ember Data 1.0-beta.8) of the DS.RESTAdapter and DS.RESTSerializer call normalizePayload with only 1 parameter. I removed the `type` parameter to fix this.

-----

Hi Dali, 

I think it's great that someone is undertaking the effort to provide some more compatibility to the JSON API specs for Ember.js. I found a few issues in your implementation, but maybe I can help out with some of them. Here's the first and most obvious bug I encountered: 

I am trying to implement this http://jsonapi.org/format/#document-url-template-shorthands, but I didn't try if this change breaks another of the JSON API formats.
Unfortunately there are no tests for this project at the moment.

Cheers!
M