Fix STM blocking on connecting

When attempting to connect to an address that doesn't exist,
startEuphConnection now doesn't result in a thread blocked by an STM
transaction any more. It now throws a simple ConnectionFailed exception.

src/EuphApi/Connection.hs

@@ -107,13 +107,16 @@ startEuphConnection host room = do
   let euphCon = Connection locked sendQueue eventQueue
   void
     $ forkIO
-    $ handle (handleException eventQueue)
+    $ handle (handleIOException eventQueue)
+    $ handle (handleHandshakeException eventQueue)
     $ WSS.runSecureClient host 443 ("/room/" ++ room ++ "/ws")
     $ recvClient euphCon
   return euphCon
   where
-    handleException :: EventQueue -> WS.HandshakeException -> IO ()
-    handleException qEvent _ = atomically $ writeTBQueue qEvent ConnectionFailed
+    handleHandshakeException :: EventQueue -> WS.HandshakeException -> IO ()
+    handleHandshakeException qEvent _ = atomically $ writeTBQueue qEvent ConnectionFailed
+    handleIOException :: EventQueue -> IOException -> IO ()
+    handleIOException qEvent _ = atomically $ writeTBQueue qEvent ConnectionFailed
 
 {-
  - Send thread