[WIP] feat(ng-pluralize): Implement the ng-pluralize directive

This is an attempt to implement #133 - It is still **a WIP**

There's still one thing I can't figure out how to do: I need to replace `{}` with someting like `{{ count - 2 }}` but `count` is interpreted as a string and then `-` triggers an error: `NoSuchMethodError : method not found: '-'`

Would someone have a hint on how to solve this ?

Todo
- [ ] Finish the implementtation
- [ ] Add tests
- [ ] Remove the modified helloworld from the PR