Hex output for bytes

[awfm9]

Currently, the bytes are returned as ASCII / code points. That's not very useful; in most cases, it would be better to have a hex encoding such as provided by the hex package of the standard library.

[rasky]

@rs I need this as well, I might end up working on a PR if we agree on the API.

My proposal is to add Hex8, Hex16, Hex32 and Hex64 wherever UintNN is used. The new hex functions would take uints of the specified size, but format then in hexadecimal format.

[rs]

Would you also have a Hex taking []byte?

[rasky]

You mean as counterpart to Bytes? Yes, that's also possible.

[rs]

Fixed by #42