Prevent losing commands orders when adding the 'help' command.

When adding the 'help' command (by using the 'add_help_cmd' parameter),
the command was added to the exising configuration and then commands were
sorted. Now, the command is added before the other commands and so the
order of commands is kept.

clg/__init__.py

@@ -447,12 +447,11 @@ def __init__(self, config, keyword='command', deepcopy=True):
                 raise CLGError([], 'unable to add help command: no subparsers')
 
             if 'parsers' in subparsers_conf:
-                subparsers_conf['parsers'].update(_HELP_PARSER)
-                subparsers_conf['parsers'] = (
-                    OrderedDict(sorted(subparsers_conf['parsers'].items())))
+                subparsers_conf['parsers'] = OrderedDict(
+                    list(_HELP_PARSER.items()) + list(subparsers_conf['parsers'].items()))
             else:
-                subparsers_conf.update(_HELP_PARSER)
-                subparsers_conf = OrderedDict(sorted(subparsers_conf.items()))
+                subparsers_conf = OrderedDict(
+                    list(_HELP_PARSER.items()) + list(subparsers_conf.items()))
             self.config['subparsers'] = subparsers_conf
 
         self._add_parser([])