1 - static hello world directive.
2 - use enclosing scope property.
3 - introduce isolate scope.
4 - import enclosing scope value via interpolated attribute
5 - establish bi-directional binding with enclosing scope property.
6 - add transclution.
7 - demonstrate compile vs. link function.
8 - Listening to event in link function - not working!
9 - "Import" out-of-Angular-world-event to Angular world with $apply.