ferris-says has undefined behavior when not using UTF-8
Affected versions receive a &[u8] from the caller through a safe API, and pass it directly to the unsafe str::from_utf8_unchecked function. The behavior of ferris_says::say is undefined if the bytes from the caller don't happen to be valid UTF-8. The flaw was corrected in ferris-says#21 by using the safe str::from_utf8 instead, and returning an error on invalid input. However this fix has not yet been published to crates.io as a …