fix Scope issues to be compatible with AngulartDart 0.9.9

AngularDart 0.9.9 contains a major overhaul to the change-detection algorithm which is used behind the scenes during scope digests. As a result, much of the scope API has changed to facilitate this new feature.

https://github.com/angular/angular.dart/blob/master/CHANGELOG.md#v099-glutinous-waterfall-2014-03-10

Thus angular.dart.ui was not compatible anymore. This commit fix this.