lz4-compress is unmaintained

[According to the developers](https://gitlab.redox-os.org/redox-os/tfs/issues/89) this crate is no longer maintained.

The suggested alternative is [`lz4-compression`](https://crates.io/crates/lz4-compression), a maintained fork of `lz4-compress`.

See also [lz-fear](https://crates.io/crates/lz-fear) which is compatible with the reference LZ4 implementation in C, but not with lz4-compress.