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

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).
Merge pull request #44 from chalin/patch-3

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