branch out RNG when measuring (dragoon/komodo!130)

- addresses #9 
- needed !133 to work

this MR simply adds `+ Clone` to `rng` and removes the `mut` from the `rng` of the `measure_inbreeding` function.

running the same snippet of code from #9 yields the following two images with a schedule of $1$ and $5$ respectively

![000_1.1](/uploads/ace74e299c6d4374df713ab5004f3c1d/000_1.1.png)
![000_1.2](/uploads/c784f5b62c41004971fd3048f7b5babc/000_1.2.png)

we see that all measurements on $t$ where $t = 0 \mod 5$ are the same in both images