docs(FormBuilder): Add missing quotes in example
docs(FormBuilder): Add missing quotes in example

Author: Benjamin Dopplinger <b.dopplinger@gmail.com>

Closes https://github.com/dart-lang/angular2/pull/72

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chalin/angular2,matanlurey/angular,chalin/angular2,matanlurey/angular,kevmoo/angular,matanlurey/angular,angulardart/angular,kevmoo/angular,kevmoo/angular,chalin/angular2,angulardart/angular,angulardart/angular