Fix absolute include path in lua-termbox.c

[purplepwny]

On line 7, you have an absolute path to termbox.h:

#include "/home/robert/coden/projects/github/termbox/src/termbox.h"

Of course, this should probably be changed to the line commented out above:

#include <termbox.h>

[lishuren]

I think it is OK as whatever you will change the line to fit your project.