pubspec.yaml: update link to API docs
pubspec.yaml: update link to API docs

Author: Patrice Chalin <pchalin@gmail.com>

Closes https://github.com/dart-lang/angular2/pull/321

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=151589494

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