Remove value attribute of text input having ng-model (Ch.5)

- Removed the `value` attribute: given that the `“name-filter”` text input is bound to the `ctrl.nameFilterString` model, the presence of the input `value` attribute seems at best useless, but is more likely to be confusing to beginners. 
- Also removed input end tag (since [input is an empty / void element](http://stackoverflow.com/questions/13232121/closing-html-input-tag-issue)).