Remove wrapError calls, fixes #3346

Ref: issue #3346 

Currently wrapError is always called before Backbone.sync. If wrapError is removed and its functionality is moved within Backbone.sync, it will provide these added benefits:

1. When users override Backbone.sync themselves, they can check to see if an error parameter was explicitly defined in their code
2. No unnecessary pre-emptive checks to see if options.error is specified on every ajax call