feat($resource): expose $promise and $response in promise-based api

This is a WIP to show a possible $resource promise-based api discussed in https://github.com/angular/angular.js/commit/dba6bc73e802fdae685a9f351d3e23c7efa8568a

Main changes:
 * $promise and $response (http response) are also exposed on resource instance object.
 * on success, the promise resolves to the same resource instance object filled with data. This is expected to be able to use in resolve section of $route.when().

I'll need to add more tests if the interface looks good.