Consider supporting CPython's random compatibility about rand_mt

[lopopolo]

Thanks for doing the legwork to find the differences between CPython's and CRuby's RNGs @ignassew! This doesn't look like that much of a burden to support. I'd love to accept a contribution to make this happen.

Let's add the CPython support and gate it behind an optional cpython feature. Can you structure the source code so it looks like this:

$ tree src
src
├── lib.rs
├── mt
│   └── rand.rs
├── mt.rs
├── mt64
│   └── rand.rs
├── mt64.rs
├── python
│   ├── mt
│   │   └── rand.rs
│   └── mt.rs
├── python.rs
├── vectors
│   ├── mt.rs
│   └── mt64.rs
└── vectors.rs

7 directories, 10 files

Let's also add a tests/python_reproducability.rs test to match the Ruby one and capture your test case in the issue description.

There's some breaking changes I've been meaning to make (for example, I think I've revisited my stance on #31 since in practice everyone, myself included, prefers the Mt type alias in code) which means it should be no problem packaging this up to crates.io.

I do like your idea on adding documentation to the README about what other languages' RNGs this crate has reproducibility guarantees with.

I'll assign this ticket to you. Looking forward to a PR 🙇