UPDATE, March 28th, 2016: Long time no blêh! But here we are again. This time to mention that in addition to what was already covered, darkness will now also touch CrabOfDoom's Bare Bones Deep Sleeper (single bed coffin only), added in response to Artemida's request.
UPDATE, March 30th, 2016: There is word that the code for CoD's Bare Bones coffin doesn't work. Please report your findings.
UPDATE, May 16th, 2016: Since nobody has corrected me, saying that the mod *does* work with the Bare Bones coffin, I've taken another look and made modifications. I do need feedback on whether or not this works for anyone.
Credits: All thanks go to Monique, who created the original version. My contribution was minor.
Additional special thanks go to the Coffin Crew.
File Updated 16-05-2016