v0.2.0

• Logging client replaced with preview version (see below).

• New clients for some of Google's Machine Learning APIs: Vision, Speech, and
  Natural Language.

• Preview version of a new [Stackdriver Logging][cloud-logging] client in
  cloud.google.com/go/preview/logging.
  This client uses gRPC as its transport layer, and supports log reading, sinks
  and metrics. It will replace the current client at cloud.google.com/go/logging shortly.