Added Simple8b RLE variant.

Thanks for the great library!
Here is a small variation on Simple8b that I did a year and a half ago but was too lazy to post here.
Obviously it can't compete with your fastest schemes, but IMO it's an improvement over stock Simple8b
in that it has faster decoding and built in potential to tightly pack/unpack highly redundant data.
I hope you can find some aspect of it interesting or at least amusing :)