README: beta release
README: beta release

Also bigquery changes.

Change-Id: If4805a444fa3a63ee1ee86c9e9fe0e634a221542
Reviewed-on: https://code-review.googlesource.com/9841
Reviewed-by: Sai Cheemalapati <36dc41adb0ea108898de35222b4f3585eb1d8968@google.com>

michael-grosshans/google-cloud-go,michael-grosshans/google-cloud-go