CSV - High performance CSV decoder for Erlang

Erlang CSV decoder (no encoder) implemented as a NIF using libcsv.

- When decoding to string, each value is returned as one item per decoded byte. E.g. a 2 byte UTF-8 character will be returned as a list with 2 elements, which can be encoded into a valid UTF-8 binary by `erlang:list_to_binary/1`.
- The `reload`, `upgrade`, `unload` callbacks are not implemented which will potentially cause crashes when hot code upgrading to a future version.

 - Add encoding support.

The MIT License (MIT). See LICENSE for details.