angular/angular.dart — pull request #684 by alorenzen (2014-03-06 00:03:51+00:00)
Title: fix(ngControl): unregister control from parent on detach

Un-register a control with its parent on detach, and also move register call to attach().
Right now, when a form element(such as an input) is removed from the dom,
the parent control does not remove it from the list of controls.