Tweak contrast for zenburn colorscheme

dotfiles/config/Xlib/colorscheme/zenburn.Xdefaults

@@ -3,7 +3,7 @@
 !## ======= ====== ##
 
 URxvt.foreground:       #dcdccc
-URxvt.background:       #3f3f3f
+URxvt.background:       #080808
 URxvt.colorUL:          #c5f779
 URxvt.underlineColor:   #c5f779
 URxvt.color0:           #3f3f3f
@@ -24,7 +24,7 @@ URxvt.color14:          #93e0e3
 URxvt.color15:          #ffffff
 
 xterm*foreground:       #dcdccc
-xterm*background:       #3f3f3f
+xterm*background:       #080808
 xterm*color0:           #353535
 xterm*color8:           #666666
 xterm*color1:           #AE4747