0.3.0

Added

• async-tftp is now runtime/executor agnostic thanks to [smol] building
  blocks. You can even run it with a simple block_on.
• Added an example on how you can serve files from a tar.gz.
• Added TftpServerBuilder::std_socket.

Changed

• Because use-tokio feature flag is removed, Handler now only accepts
  futures_io::AsyncRead and futures_io::AsyncWrite.
• TftpServerBuilder::socket now accepts async_io::Async<std::net::UdpSocket>.

Removed

• Removed use-async-std feature flag.
• Removed use-tokio feature flag.
• Removed async_tftp::log::set_log_level.