Added localStorageService.bind

Added localStorageService.bind to get a value from local storage and watch for changes.  Please consider.

Usage:

```
localStorageService.bind($scope,'key',{defaultValue});
```
$watchCollection from documentation: "Shallow watches the properties of an object and fires whenever any of the properties change (for arrays, this implies watching the array items; for object maps, this implies watching the properties)".
This means that if I change a "deeper" object, the listener is not fired. 

The fix is using `$watch` with `objectEquality == true`:
```
scope.$watch(key, function(newVal) {
  addToLocalStorage(key, newVal);
}, true);
```