Adapted code to work with the current and official Google PHP API Client[1]

- changed requirement in composer.json
- changed class names to match the new library structure
- removed conditional in \Thujohn\Analytics\Analytics::getAllSitesIds()
  (maintaining compatibility with the new Google API Client)

  [1] (https://github.com/google/google-api-php-client)
Adapted requirement
Merge pull request #9 from mjaschen/official_google_api_client

Use the official Google API Client