Bump version to 2.2.1

Bump version to v2.2.0

Update to v2.1.1

Bump Podspec version to 2.1.0

Update README.md for 2.0.0

Adjust event ordering such that the previous state gets a did exit ev…

…ent before the new state gets a did enter

Bump Podspec to 1.1.0

Initial check-in of TransitionKit