Backone 1.0 compatibity

Looks like there is an undocumented change in Backbone 1.0's sync.

Existing version of backfire just doesn't work, after a while I found that the call back responses parameters changed. 

I made the changes based on similar fix on Backbone.localStorage
https://github.com/jeromegn/Backbone.localStorage/commit/bd34c367442f6854c0d5664425ec04c8108a69fe