Change the way we fetch multiple posts by ID

JSON-API specifies that multiple resources should be fetched with a
comma-separated list of IDs, i.e. discussions/1,2,3,4. But this is
problematic because if we do a findQuery with only one ID, then a
single object will come back from the API where the serializer is
expecting an array containing a single object.

Instead, I’ve just implemented an ids “filter” on the discussions index
API route (which is the default way that the adapter finds multiple
IDs.)

ember/app/serializers/application.js

@@ -1,4 +1,5 @@
 import JsonApiSerializer from 'ember-json-api/json-api-serializer';
+
 export default JsonApiSerializer.extend({
 	normalize: function(type, hash, property) {
 		var json = {};