Prepare v0.45.1 (googleapis#751)

* Prepare v0.45.1

* add note to throws annotation

Prepare v0.45.0 (googleapis#748)

Prepare v0.44.0 (googleapis#744)

Prepare v0.43.1 (googleapis#743)

Prepare v0.43.0 (googleapis#736)

Prepare v0.42.0 (googleapis#728)

Prepare v0.41.0 (googleapis#722)

* Prepare v0.41.0

* Don't report code coverage on hhvm

* Update google/gax and google/proto-client dependency versions

Prepare v0.40.0 (googleapis#705)

Prepare v0.39.2 (googleapis#678)

Prepare v0.39.1 (googleapis#671)