v1.15.0

Added

• Added modelType option to translateText() to use models with higher
  translation quality (available for some language pairs), or better latency.
  Options are 'quality_optimized', 'latency_optimized', and 'prefer_quality_optimized'
• Added the modelTypeUsed field to translateText() response, that
  indicates the translation model used when the modelType option is
  specified.