Defines default Backbone.sync options parameter

The mocked behavior is inconsistent with Backbone's actual behavior.  Backbone.sync's `options` parameter defaults to an empty object when the caller does not supply it: https://github.com/jashkenas/backbone/blob/master/backbone.js#L1134
Sets default values for emulateHTTP and emulateJSON in overridden Backbone.sync method.
Merge pull request #12 from jeremyckahn/patch-1

Defines default Backbone.sync options parameter