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
chore($http): remove deprecated responseInterceptors functionality

Code cleanup! response interceptors have been deprecated for some time, and it is confusing to have
two APIs, one of which is slightly "hidden" and hard to see, which perform the same task. The newer
API is a bit cleaner and more visible, so this is naturally preferred.

BREAKING CHANGE:

Previously, it was possible to register a response interceptor like so:

    // register the interceptor as a service
    $provide.factory('myHttpInterceptor', function($q, dependency1, dependency2) {
      return function(promise) {
        return promise.then(function(response) {
          // do something on success
          return response;
        }, function(response) {
          // do something on error
          if (canRecover(response)) {
            return responseOrNewPromise
          }
          return $q.reject(response);
        });
      }
    });

    $httpProvider.responseInterceptors.push('myHttpInterceptor');

Now, one must use the newer API introduced in v1.1.4 (4ae46814), like so:

    $provide.factory('myHttpInterceptor', function($q) {
      return {
        response: function(response) {
          // do something on success
          return response;
        },
        responseError: function(response) {
          // do something on error
          if (canRecover(response)) {
            return responseOrNewPromise
          }
          return $q.reject(response);
        }
      };
    });

    $httpProvider.responseInterceptors.push('myHttpInterceptor');

Closes #7266