0.2.4: language changes.
0.2.4: language changes.

`MaybeOwned` has been superseded by `CowString`. That really doesn't
affect rust-encoding, as it used `SendStr` which now refers to
a specialization of `CowString`, but it has also removed
`IntoMaybeOwned` so we needed to update.

nox/rust-encoding,tempbottle/rust-encoding,lifthrasiir/rust-encoding,nox/rust-encoding,tempbottle/rust-encoding,nox/rust-encoding,tempbottle/rust-encoding,lifthrasiir/rust-encoding,lifthrasiir/rust-encoding