echoes 0.2.0

Echoes is a pure-Ruby macOS terminal emulator with first-class integrations for rubish (in-process shell) and rvim (in-process vim editor) panes, plus a private OSC namespace for in-pane Ruby tools that want to drive UI features (gradient backgrounds, rectangular fills, proportional-font text) other terminals can't. Written in pure Ruby on top of AppKit via Fiddle.