v0.3.0

Highlights

• New async client: split out a protocol module and added an async SFTP client (#13, #14).
• Optional russh backend for the async client behind the russh feature.
• Interactive sftp binary: new CLI backed by an ssh subprocess, under the default bin feature.
• Expanded test coverage across the codec and client, including two bug fixes surfaced by the new tests.
• Bumped ssh2 to 0.9.5.

Features

• bin (default): interactive sftp CLI using rustyline + shell-words.
• ssh2: sync client over ssh2.
• async: async client over tokio.
• russh: async client with russh transport (implies async).