Arrow keys support (issue 44)

[grota]

This is my first try at implementing the feature request I made here: https://github.com/sjbach/lusty/issues/44

I had to disable the <Esc> mapping because the `, ,

` keys send a 3-char sequence starting with `^[`  followed by O and then by A,B,C or D. Works for me because I don't use `` to get out of lusty. Instead I use ``. There's probably a better way.

[grota]

ok, here's the updated code, this works better. It only maps the arrow keys and Esc keeps working.

[grota]

ok, the source files have been modified too

[sjbach]

Merged - thanks!