correct spacing on special keys

Always add space between special keys (like modifiers or Esc) and
alphanumerical oneletter symbols.
correct way to handle modifiers based on event state
<= for backspace key
keep pos option, bg and fg cmd flags, fix quit

* KEEP_POS is not by default, means user can drag window wherever one
  wants;
* background and foreground colors can be changed via command line
  flags;
* process will be terminated no matter how it's closed (bug in Xlib impl);
use python2
visual space character