added more special keys
Created by: IGI-111
This should partly solve #16
Key now supports Home, End, PageUp, PageDown, Delete, Insert and
Function keys. All this is done through the detection of both VT100
escape codes and more modern standard counterparts.
For instance, F2 can be both ESC OQ
on VT100, screen, and some versions of xterm and ESC [12~
on rxvt and other xterm versions depending on your terminal.
Note also that only F1 through F12 are supported since codes tend to wildly diverge beyond that point and it's not part of the ISO or ANSI keyboard specs anyways.