chore: release v2.1.0 (googleapis#204)

chore: Release v2.0.0 (googleapis#189)

* chore: release v2.0.0

* Add compatibility notice to 1.7.0 release notes.

* Fix typo in pull request URL in CHANGELOG.

chore: release v1.7.0 (googleapis#154)

chore: release 1.6.1 (googleapis#125)

* updated CHANGELOG.md [ci skip]

* updated setup.cfg [ci skip]

* updated setup.py

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>

chore: release 1.6.0 (googleapis#117)

## [1.6.0](https://www.github.com/googleapis/python-pubsub/compare/v1.5.0...v1.6.0) (2020-06-09)

### Features

* Add flow control for message publishing ([googleapis#96](https://www.github.com/googleapis/python-pubsub/issues/96)) ([06085c4](https://www.github.com/googleapis/python-pubsub/commit/06085c4083b9dccdd50383257799904510bbf3a0))


### Bug Fixes

* Fix PubSub incompatibility with api-core 1.17.0+ ([googleapis#103](https://www.github.com/googleapis/python-pubsub/issues/103)) ([c02060f](https://www.github.com/googleapis/python-pubsub/commit/c02060fbbe6e2ca4664bee08d2de10665d41dc0b))


### Documentation
- Clarify that Schedulers shouldn't be used with multiple SubscriberClients ([googleapis#100](googleapis#100)) ([cf9e87c](googleapis@cf9e87c))
- Fix update subscription/snapshot/topic samples ([googleapis#113](googleapis#113)) ([e62c38b](googleapis@e62c38b))


### Internal / Testing Changes
- Re-generated service implementaton using synth: removed experimental notes from the RetryPolicy and filtering features in anticipation of GA, added DetachSubscription (experimental) ([googleapis#114](googleapis#114)) ([0132a46](googleapis@0132a46))
- Incorporate will_accept() checks into publish() ([googleapis#108](googleapis#108)) ([6c7677e](googleapis@6c7677e))

chore: release 1.5.0 (googleapis#88)

* updated CHANGELOG.md [ci skip]

* updated setup.cfg [ci skip]

* updated setup.py [ci skip]

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>

chore: release 1.4.3 (googleapis#71)

* updated CHANGELOG.md [ci skip]

* updated setup.cfg [ci skip]

* updated setup.py [ci skip]

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>

chore: release 1.4.2 (googleapis#56)

* updated CHANGELOG.md [ci skip]

* updated setup.cfg [ci skip]

* updated setup.py [ci skip]

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>

chore: release 1.4.1 (googleapis#54)

* updated CHANGELOG.md [ci skip]

* updated setup.cfg [ci skip]

* updated setup.py [ci skip]

* Update CHANGELOG.md

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>
Co-authored-by: Prad Nelluru <pradn@google.com>

chore: release 1.4.0 (googleapis#42)

* updated CHANGELOG.md [ci skip]

* updated setup.py [ci skip]

Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>