Freshen crate, fix to/from_base64

[Jake-Shadle]

This change went further than initially expected, feel free to ask me to split it up into smaller PRs if you want!

• FIX: Bitvec's to_bytes pads bits to the next byte, the test wasn't catching that this was a problem because the number of bits for the hash were divisible by 8, this just adds the number of padding bits into the top bits of the header byte that was being used for the HasherType so that the bitvec has the correct length after deserialization.
• Add support for the latest version of image (0.22.2) - Fairly minor update
• Bump rand to 0.7.0 - Only used by tests, so figured this was fine
• Rustformatted and fixed all the clippy lints