Bumped version to 2.9.1 (firebase#137)

* Bumped version to 2.9.1

* Changlog updates

* Changlog url

* trigger cla check

Bumped version to 2.9.0 (firebase#129)

Bumped version to 2.8.0 (firebase#116)

Bumped version to 2.7.0 (firebase#106)

Bumped version to 2.6.0 (firebase#102)

Bumped version to 2.5.0 (firebase#92)

Bumped version to 2.4.0 (firebase#76)

Bumped version to 2.3.0 (firebase#68)

Bumped version to 2.2.0

Bumped version to 2.1.1 (firebase#52)