Support for Rand v0.8

[alechenthorne]

Simply upgrading the dependency to Rand v0.8 doesn't work as it seems the rand::AsBytesSliceMut trait has been removed and more info can be seen in this comment.

This requires for gen_biguint to move to using the higher level fill method rather than the fill_bytes method on the data.

I have a working example, but would be curious the thoughts on using fill directly.

[phayes]

I have a PR for this here: #25

[dignifiedquire]

Still waiting a little bit longer to propagate this through libraries, breaking rand changes are quite painful and dividing in the ecosystem. Last time around it took months for the ecosystem to rally behind the latest version.

[phayes]

One approach could be to track a separate alpha branch that contains the updated rand as an interim measure. It looks like this is the approach that the dalek-cryptography folks will be taking (dalek-cryptography/curve25519-dalek#338). It's worth noting that curve25519 is related to num-bigint-dig via num-bigint-dig <- pgp -> ed25519-dalek -> curve25519-dalek.

[dignifiedquire]

I don't think I'll want an extra release cycle, I'll probably merge it soonish to master and then do a release once things are looking good.

[sabify]

@dignifiedquire Would you mind to release the update for crate.io due to latest changes for support rand 0.8?

[dignifiedquire]

Released 0.7 with rand@0.8 support

[sabify]

Thanks!