Adding url shortener api example.

Shorten and Expand work. The example throw exception on analytics and history.

```
Failed to load resource: the server responded with a status of 401 (Unauthorized)
  https://www.googleapis.com/urlshortener/v1/url/history
Failed to load resource: the server responded with a status of 401 (Unauthorized)
  https://www.googleapis.com/urlshortener/v1/url/history
Exception: FutureUnhandledException: exception while executing Future
  APIRequestException: 401 Login Required
original stack trace:
  null
Stack Trace: #0      _FutureImpl._complete (bootstrap:844:11)
#1      _FutureImpl._complete (bootstrap:848:5)
#2      _FutureImpl._setException (bootstrap:873:14)
#3      _CompleterImpl.completeException (bootstrap:952:30)
#4      UrlResource.list.<anonymous closure> (http://127.0.0.1:3030/Users/adam/dart/dart_api_generator_tests/web/urlshortener_v1/packages/urlshortener_v1_api_client/src/resources.dart:130:56)
#5      _FutureImpl._complete (bootstrap:832:22)
#6      _FutureImpl._complete (bootstrap:848:5)
#7      _FutureImpl._setException (bootstrap:873:14)
#8      _CompleterImpl.completeException (bootstrap:952:30)
#9      Client._request.<anonymous closure> (http://127.0.0.1:3030/Users/adam/dart/dart_api_generator_tests/web/urlshortener_v1/packages/urlshortener_v1_api_client/src/client.dart:154:38)

```