Override put, get, swap to receive context (#221)

* override get,put,swap to add context

Re-add state monad (#210)

* re-add state monad

Set version to 2.2.0

Set version to 2.1.0

Set version to 2.0.0.

Set version to 1.2.1

Update version

Set version to 1.1.0.

Separate features, bugfixes and backward incompatible changes in chan…

…gelog