Crate evaluation for 2017-07-25: rand

Ok, just one more extreme idea. It seems viable to rename this crate to oldrand, change this crate to be nothing but the content of ring’s rand module (though maybe renaming SecureRandom to Random), and leaving all other conveniences to battle it out as experiments in other crates (though I do think we would immediately need that polymorphic random function somewhere). Then we would have a stronger foundation at the source of random number generation, and have room to breath about all the other features people might want.