In fact I think that we should show both, explaining pros / cons:
- `@` - can easily observe but need to parseInt
- `&` - can use any JavaScript type, not constrained to String

I've also wanted to show the `&` as a getter which is useful if we want to:
* preserve JavaScript type
* indicate a read-only attribute
At the end of the day this is just short-hand for manually invoking $parse