Check that results are consistent across different architectures and machines

[ianhinder]

In particular, check that the RNG is portable. The code seems to use rand. The results of this are not portable; e.g. macOS' std C library has a different algorithm to glibc. Possibly the C++ RNGs are more portable; I'm not sure.

[richardreeve]

I had to update Distributions.jl a while ago so that all distributions could handle a first argument RNG to make it thread safe. So we should be using that everywhere, such as here, and we set up RNGs here as MersenneTwisters, so unless the code is inconsistent between architectures for that RNG, we should be okay I think?

[ianhinder]

@richardreeve, you replied to a CoronaBICI issue. Need to get per-label notifications working!