Update aes version

[xpepermint]

This crate depends on aes = "^0.7" and thus doesn't work with the latest aes = "0.8.1".

[daira]

In zcash/librustzcash#757 I recommend the following for fpe, to help to reduce duplicate crate dependencies in Zcash:

• depend on cipher 0.4 instead of cipher 0.3
• depend on aes 0.8 instead of aes 0.7
• replace the dependency on block-modes 0.8, which says: "This crate is deprecated. Use crates from https://github.com/RustCrypto/block-modes instead." Based on this I think it probably wants cbc 0.1 (which depends on cipher 0.4.2 and aes 0.8).

Note that cipher 0.4 (and hence aes 0.8) has incompatible API changes.

[rohitjoshi]

Any update on this?