Seeded random crate

[matteojug]

For seeded random, is there a specific reason you used seeded-random? It doesn't seem a very popular crate, was it vetted somehow?

[NikitaMasych]

We need cryptographically secure and portable random generator, thus we relied on this crate instead of StdRng for example; it is just a convenient wrapper around rand_chacha. Yet indeed, you are correct that it is not really maintable (for instance link to repo is wrong), so I changed it to use rand_chacha directly in #18