docs(changelog): release notes for 1.3.0-beta.7 proper-attribution
docs(tutorial/step-12): add info about app.css changes

Closes https://github.com/angular/angular-phonecat/issues/145
docs(tutorial/step-3): fix experiments

Closes https://github.com/angular/angular-phonecat/issues/142
chore(jshint): enforce jshint for tests

Closes #7264