Allow 640 permissions

Fixes #1

go-sendxmpp.go

@@ -86,10 +86,10 @@ func parseConfig(configPath string) (configuration, error) {
 	// Only check file permissions if we are not running on windows.
 	if runtime.GOOS != "windows" {
 		info, _ := os.Stat(configPath)
-		// Check for file permissions. Must be 600 or 400.
+		// Check for file permissions. Must be 600, 640 or 400.
 		perm := info.Mode().Perm()
 		permissions := strconv.FormatInt(int64(perm), 8)
-		if permissions != "600" && permissions != "400" {
+		if permissions != "600" && permissions != "640" && permissions != "400"  {
 			return output, errors.New("Wrong permissions for " + configPath + ": " +
 				permissions + " instead of 400 or 600.")
 		}