Support for Rand 0.9

[sarsko]

Rand updated their APIs in 0.9: https://github.com/rust-random/rand/releases/tag/0.9.0. We should update our APIs accordingly so that it is easy for users to upgrade their Rand dependency (or use Shuttle with a project which uses Rand 0.9). I think the easiest might be to offer both the 0.9 and the 0.8 API. One alternative is to "cratify" this functionality; have a ShuttleRand crate at version 0.8, and a ShuttleRand crate 0.9, and then let users import accordingly.