v0.20.0

• bigquery: Support SchemaUpdateOptions for load jobs.

• bigtable:

  • Add SampleRowKeys.
  • cbt: Support union, intersection GCPolicy.
  • Retry admin RPCS.
  • Add trace spans to retries.

• datastore: Add OpenCensus tracing.

• firestore:

  • Fix queries involving Null and NaN.
  • Allow Timestamp protobuffers for time values.

• logging: Add a WriteTimeout option.

• spanner: Support Batch API.

• storage: Add OpenCensus tracing.