Update to transformers-0.5.6.2

0.5.6.2 Ross Paterson Feb 2019
* Further backward compatability fix

0.5.6.1 Ross Paterson Feb 2019
* Backward compatability fix for MonadFix ListT instance

0.5.6.0 Ross Paterson Feb 2019
* Generalized type of except
* Added Control.Monad.Trans.Writer.CPS and Control.Monad.Trans.RWS.CPS
* Added Contravariant instances
* Added MonadFix instance for ListT

0.5.5.0 Ross Paterson Oct 2017
* Added mapSelect and mapSelectT
* Renamed selectToCont to selectToContT for consistency
* Defined explicit method definitions to fix space leaks
* Added missing Semigroup instance to `Constant` functor

0.5.4.0 Ross Paterson Feb 2017
* Migrate Bifoldable and Bitraversable instances for Constant

0.5.3.1 Ross Paterson Feb 2017
* Fixed for pre-AMP environments

0.5.3.0 Ross Paterson Feb 2017
* Added AccumT and SelectT monad transformers
* Deprecated ListT
* Added Monad (and related) instances for Reverse
* Added elimLift and eitherToErrors
* Added specialized definitions of several methods for efficiency
* Removed specialized definition of sequenceA for Reverse
* Backported Eq1/Ord1/Read1/Show1 instances for Proxy

0.5.2.0 Ross Paterson Feb 2016
* Re-added orphan instances for Either to deprecated module
* Added lots of INLINE pragmas

0.5.1.0 Ross Paterson Jan 2016
* Bump minor version number, required by added instances

0.5.0.2 Ross Paterson Jan 2016
* Backported extra instances for Identity

0.5.0.1 Ross Paterson Jan 2016
* Tightened GHC bounds for PolyKinds and DeriveDataTypeable

0.5.0.0 Ross Paterson Dec 2015
* Control.Monad.IO.Class in base for GHC >= 8.0
* Data.Functor.{Classes,Compose,Product,Sum} in base for GHC >= 8.0
* Added PolyKinds for GHC >= 7.4
* Added instances of base classes MonadZip and MonadFail
* Changed liftings of Prelude classes to use explicit dictionaries

0.4.3.0 Ross Paterson Mar 2015
* Added Eq1, Ord1, Show1 and Read1 instances for Const

(pho)