[Documentation Issue] python example code seems out of date #1242

Page Name: bigquery-usage
Release: 0.8.0

When I ran example code with current version of gcloud library(0.8.0), this error is occured.

Traceback (most recent call last):
  File "bigquery_test.py", line 6, in <module>
    result = client.query(query, timeout_ms=1000)
AttributeError: 'Client' object has no attribute 'query'

and query method is seems splited into run_async_query and run_sync_query.
But this document still use not existed query method with polling approach for synchronous execution.

Exporting data (async) section also has same problem.
table.export_to_storage method is move to Client.extract_table_to_storage with different arguments.