Log Message:
Update to 2.2.1

CHANGELOG:
2.2.1
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* Provide MINIMAL pragmas for `MonadState`, `MonadWriter`, `MonadReader`
* Added a cyclic definition of `ask` in terms of `reader` for consistency with \ 
`get`/`put` vs. `state` and `tell` vs. `writer`
* Fix deprecation warnings caused by `transformers` 0.4 deprecating `ErrorT`.
* Added `Control.Monad.Except` in the style of the other `mtl` re-export modules