def add(self, path, default_handler = None, **http_methods):
        """
        Add a selector mapping.

        add(path, default_handler, **named_handlers)

        Adding order is important. Firt added = first matched.
        If you want to hand special case URI handled by one app and shorter
        version of the same regex string by anoter app,
        .add() special case first.

        Inputs:
         path - A regex string. We will compile it.
          Highly recommend using grouping of type: "(?P<groupname>.+)"
          These will be exposed to WSGI app through environment key
          per http://www.wsgi.org/wsgi/Specifications/routing_args

         default_handler - (optional) A pointer to the function / iterable
          class instance that will handle ALL HTTP methods (verbs)

         **named_handlers - (optional) An unlimited list of named args or
          an unpacked dict of handlers allocated to handle specific HTTP
          methods (HTTP verbs). See "Examples" below.

        Matched named method handlers override default handler.

        If neither default_handler nor named_handlers point to any methods,
        "Method not implemented" is returned for the requests on this URI.

        Examples:
        selectorInstance.add('^(?P<working_path>.*)$',generic_handler,
                              POST=post_handler, HEAD=head_handler)

        custom_assembled_dict = {'GET':wsgi_app_a,'POST':wsgi_app_b}:
        ## note the unpacking - "**" - of the dict in this case.
        selectorInstance.add('^(?P<working_path>.*)$', **custom_assembled_dict)


        If the string contains '\?' (escaped ?, which translates to '?' in
        non-regex strings) we understand that as "do regex matching on
        QUERY_PATH + '?' + QUERY_STRING"

        When lookup matches are met, results are injected into
        environ['wsgiorg.routing_args'] per
        http://www.wsgi.org/wsgi/Specifications/routing_args
        """
        if default_handler:
            methods = defaultdict(lambda: default_handler, http_methods.copy())
        else:
            methods = http_methods.copy()
        self.mappings.append((re.compile(path.decode('utf8')), methods, (path.find(r'\?')>-1) ))