Bumped version to 2.2.0

Bumped version to 2.1.1 (firebase#52)

Bumped version to 2.1.0 (firebase#41)

Updating README (firebase#25)

* Updating README

Bumped version to 1.0.0 (firebase#16)

* Bumped version to 1.0.0

* Fixed typo in docstring