Bumped version to 2.12.0 (firebase#181)

* Bumped version to 2.12.0

* Updated changelog

Bumped version to 2.11.0 (firebase#174)

* Bumped version to 2.11.0

* Removing redundant whitespace

Bumped version to 2.10.0 (firebase#153)

 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)