apply callback invocation, in find method

I was working through the simpleBlog example in the Backbone.js Blueprints book when I noticed that the models were not being extracted from the simpleBlogPosts.json. I tracked down the cause of the bug on line 144 of bourne.js:

     callback(null, data); 

The callback was being invoked with null as its context. Either callback(data) or callback.apply(null, data) should work.