Release google-cloud-pubsub 0.38.1 (googleapis#3731)

* Add endpoint argument to constructor

Release google-cloud-trace 0.34.5 (googleapis#3719)

* Fix max threads setting in thread pools
  * Thread pools once again limit the number of threads allocated.
* Update documentation links

Release google-cloud-spanner 1.9.5 (googleapis#3714)

* Reduce thread usage at startup
  * Allocate threads in pool as needed, not all up front
* Update documentation links

Release google-cloud-pubsub 0.38.0 (googleapis#3715)

* Allow persistence_regions to be set
  * Support setting persistence_regions on topic creation
    and topic update.
* Allow Service endpoint to be configured
  * Google::Cloud::PubSub.configure.endpoint
* Fix max threads setting in thread pools
  * Thread pools once again limit the number of threads allocated.
* Reduce thread usage at startup
  * Allocate threads in pool as needed, not all up front
* Update documentation links

Release google-cloud-logging 1.6.6 (googleapis#3718)

* Fix max threads setting in thread pools
  * Thread pools once again limit the number of threads allocated.
* Update documentation links

Release google-cloud-error_reporting 0.31.7 (googleapis#3717)

* Fix max threads setting in thread pools
  * Thread pools once again limit the number of threads allocated.
* Update documentation links

Release google-cloud-debugger 0.33.7 (googleapis#3716)

* Fix max threads setting in thread pools
  * Thread pools once again limit the number of threads allocated.
* Update documentation links

Release google-cloud-bigquery 1.13.0 (googleapis#3713)

* Add Table#require_partition_filter
* List jobs using min and max created_at
* Reduce thread usage at startup
  * Allocate threads in pool as needed, not all up front
* Update documentation links

Release google-cloud-firestore 1.0.0 (googleapis#3666)

* Bump release level to GA.
* Update READMEs for Firestore GA
* Update synth.py for Firestore GA in doc link
* Update google-cloud-firestore dependency to ~> 1.0 in google-cloud.gemspec

Release google-cloud-dns 0.30.1 (googleapis#3667)

* Ensure use of a sufficiently recent REST client with the correct endpoint.