Add support to new Azure Cognitive Services API

[tlehoux]

This pull request has been made in order to support for new Azure Cognitive Services API. The API calls are all the same except for how the 10-minute auth token is fetched. It now uses a single api_key to fetch the token (instead of using a client_id and client_key).

More information here: https://blogs.msdn.microsoft.com/translation/2017/04/10/reminder-move-translator-api-subscriptions-from-datamarket-to-azure-before-april-30-2017/