Stacktrace when transversing the menu on Gentoo

Interesting catch from Toralf. I'm not entirely sure if this is it but if he
was using python3 it makes sense that keys() provides an iterator whereas
reversed() expects a collection. Not able to repro it though so not sure if
this is what's at play...

  Traceback (most recent call last):
    File "./run_nyx", line 14, in <module>
      nyx.main()
    File "/root/nyx/nyx/__init__.py", line 147, in main
      nyx.starter.main()
    File "/root/nyx/stem/util/conf.py", line 289, in wrapped
      return func(*args, config = config, **kwargs)
    File "/root/nyx/nyx/starter.py", line 94, in main
      nyx.curses.start(nyx.draw_loop, acs_support = config.get('acs_support', True), transparent_background = True, cursor = False)
    File "/root/nyx/nyx/curses.py", line 216, in start
      curses.wrapper(_wrapper)
    File "/usr/lib64/python3.4/curses/__init__.py", line 94, in wrapper
      return func(stdscr, *args, **kwds)
    File "/root/nyx/nyx/curses.py", line 214, in _wrapper
      function()
    File "/root/nyx/nyx/__init__.py", line 192, in draw_loop
      nyx.menu.show_menu()
    File "/root/nyx/nyx/menu.py", line 203, in show_menu
      menu = _make_menu()
    File "/root/nyx/nyx/menu.py", line 243, in _make_menu
      submenu = panel.submenu()
    File "/root/nyx/nyx/panel/log.py", line 273, in submenu
      [RadioMenuItem(opt, filter_group, opt) for opt in self._filter.latest_selections()],
    File "/root/nyx/nyx/log.py", line 432, in latest_selections
      return list(reversed(self._past_filters.keys()))
  TypeError: argument to reversed() must be a sequence