Use a Map instead of list of tuples for commInfo

It's a bit closer to a dictionary.

ipython-kernel/src/IHaskell/IPython/EasyKernel.hs

@@ -178,7 +178,7 @@ replyTo config _ _ CommInfoRequest{} replyHeader =
   return
     CommInfoReply
       { header = replyHeader
-      , commInfo = [] }
+      , commInfo = mempty }
 
 replyTo config _ interface ShutdownRequest { restartPending = pending } replyHeader = do
   liftIO $ writeChan (shellReplyChannel interface) $ ShutdownReply replyHeader pending

ipython-kernel/src/IHaskell/IPython/Types.hs

@@ -306,7 +306,7 @@ data Message =
              -- | A response to a CommInfoRequest.
                CommInfoReply
                  { header   :: MessageHeader
-                 , commInfo :: [(String, String)] -- ^ A dictionary of the comms, indexed by uuids.
+                 , commInfo :: Map String String -- ^ A dictionary of the comms, indexed by uuids.
                  }
              |
              -- | A request from a frontend to execute some code.

main/Main.hs

@@ -267,7 +267,7 @@ replyTo _ CommInfoRequest{} replyHeader state =
   return
     (state, CommInfoReply
               { header = replyHeader
-              , commInfo = []
+              , commInfo = mempty
               })
 
 -- Reply to a shutdown request by exiting the main thread. Before shutdown, reply to the request to