Wicher Malten

I wrote the Rabbit code with the set $\{0,\ldots ,m-1\}$ in mind (and Möbius follows this), so $-20 \equiv m - 20$ which will be larger than $10$. If instead...

@Amaimaya I'm hoping it's correct now for the power-of-two modulus setting; I'll make more edits tomorrow. @mkskeller Thanks! That sounds sensible.