Added --char-scale option for fun with char edge printing
Edge finding now samples negative space on both sides of the subject and finds each edge according to its adjacent negative space. This would work with a gradient or slightly uneven background more effectively. Added an option to highlight the left edge of the subject green and the right edge red for debugging.
Added a function to combine images on either the horizontal or vertical axis. Edge finding should perhaps happen BEFORE images are combined. This makes the argument parsing more straightforward. Added arguments so that nothing is done unless the user specifically asks for it.