Fixes issue #1, an off-by-one error in img slicing
Fixes issue #1, an off-by-one error in img slicing

* Column slicing had an off-by-one error that meant some 1-px wide
columns weren't checked for foreground/background edges. This is fixed.
* The slicing of contiguous rows was more complex than it needed to be.

TadLeonard/crash-kiss,TadLeonard/crash-kiss,TadLeonard/crash-kiss