Optional deserialize function for binding

Something like this would be useful to store and deserialize complex objects like dates using "bind". 
 For example: 
```javascript
var dateRange = { 
  start: new Date(2014, 0, 1), 
  end: new Date(2014, 8, 1) 
}

localStorageService.bind($scope, "dateRange", dateRange, function (value) {
  return {
    start: new Date(value.start);
    end: new Date(value.end);
  };
});
```