Run the command `cargo +nightly fmt` to fix formatting issues.
The formatter got confused in one place, adding an incorrect
indentation, this was manually fixed.
Clippy default settings seemed to have changed introducing a few new
warnings.
warning: variable does not need to be mutable
warning: deref on an immutable reference
warning: returning the result of a `let` binding from a block
Fix them all in a single patch because CI has to pass for each patch.
`Default` was pointless, so it was replaced with internal
`from_raw_parts` method which also checks the length.
This commit also documents changes to `SerializedSignature`.
Closes#454
This de-clutters the code and prepares for the next step of adding
`IntoIterator`. The type is still re-exported so the change is neither
breaking nor inconvenient.
This also adds more datialed explanation of `SerializedSignature` and
why it's needed.