v0.45.0

• compute/metadata:
  • Add Email method.
• storage:
  • Fix duplicated retry logic.
  • Add ReaderObjectAttrs.StartOffset.
  • Support reading last N bytes of a file when a negative range is given, such
    as obj.NewRangeReader(ctx, -10, -1).
  • Add HMACKey listing functionality.
• spanner/spannertest:
  • Support primary keys with no columns.
  • Fix MinInt64 parsing.
  • Implement deletion of key ranges.
  • Handle reads during a read-write transaction.
  • Handle returning DATE values.
• pubsub:
  • Fix Ack/Modack request size calculation.
• logging:
  • Add auto-detection of monitored resources on GAE Standard.