localSync returns attributes like Backbone.sync, not a model

Fixes #32

localsync should be returning attributes, not a model, because it should
emulate how Backbone.sync acts. Unlike $.ajax, window.Store must receive
and return the model, not its attributes, since it must be able to
modify the correct idAttribute as specified by the model. Therefore it
must be localsync's responsibility to change the return value.
Add spec to reproduce #32

localsync should be receiving models, not attributes.
Formatting: Clarify conditional intent by splitting onto multiple lines
localsync create always returns the model

When using localStorage only (ignoreCallbacks will be false),
the response sent to the callback and used as a return value
was false for the create method unless options.dirty was true.
Merge branch 'localsync-returns-attributes'
Merge remote-tracking branch 'upstream/master'

Conflicts:
	backbone.dualstorage.js
	spec/backbone.dualstorage.js