2.2

• transformers 0.4 support
• Added instances for ExceptT
• Added modify' to Control.Monad.State.*

2.1.3.1

• Avoid importing Control.Monad.Instances on GHC 7.8 to build without deprecation warnings.

2.1.3

• Removed the now-irrelevant Error constraint from the MonadError instance for Either e.