Sort informations in best model VO file

When a best model is saved to a VO-table XML file, the SED information
and parameters stored in the file "headers" are now alphabetically
sorted.

pcigale/sed/io/vo.py

@@ -79,7 +79,7 @@ def save_sed_to_vo(sed, filename, norm=1.):
         votable.infos.append(Info(name="Galaxy mass in Msun", value=norm))
     votable.infos.append(Info(name="Redshift",
                               value=sed.info['universe.redshift']))
-    for name, value in sed.info.items():
+    for name, value in sorted(sed.info.items()):
         if name in sed.mass_proportional_info:
             votable.infos.append(Info(name=name, value=norm * value))
         else: