Updated awesome

  * added scratchdrop.lua, for future reference and playing;
  * rc.lua: use updated version of 'run_once' function, use 'custom'
    wallpaper, added one more tag, experimental code to start 'urxvtc'
    on first tag (not tested!).

Signed-off-by: Vladimir Lomov <lomov.vl@gmail.com>