Add support for ExceptT in Pipes.Lift

This depends on the version of `mmorph` that is in GitHub which provides instances for `ExceptT`.

There is no `liftCatchExcept` as it would be exactly the same as `liftCatchError`. `catchExcept` is a bit more general than its `catchError` counterpart in that it the error type can change.


There's no urgency to merge this from my side, I just had some spare minutes and decided to add this and send a pull request.