fix transformers 0.4 compatibility problem

pontarius-xmpp.cabal

@@ -64,7 +64,7 @@ Library
                , stringprep           >=1.0.0
                , text                 >=0.11.1.5
                , tls                  >=1.2
-               , transformers         >=0.4
+               , transformers         >=0.3
                , unbounded-delays     >=0.1
                , void                 >=0.5.5
                , x509-system          >=1.4

source/Network/Xmpp/Concurrent/IQ.hs

@@ -9,7 +9,7 @@ import           Control.Concurrent (forkIO)
 import           Control.Concurrent.STM
 import           Control.Concurrent.Thread.Delay (delay)
 import           Control.Monad
-import           Control.Monad.Except
+import           Control.Monad.Error
 import           Control.Monad.Trans
 import qualified Data.Map as Map
 import           Data.Maybe