js/libs/ember-data.js
function(data, type, record, options) {
    var root = Ember.String.decamelize(type.typeKey);
    data[root] = this.serialize(record, options);
  }
function(data, type, record, options) {
    var root = Ember.String.decamelize(type.typeKey);
    data[root] = this.serialize(record, options);
  }
Underscores the JSON root keys when serializing.

@method serializeIntoHash
@param {Object} hash
@param {subclass of DS.Model} type
@param {DS.Model} record
@param {Object} options