Update README.md

travis: Set up Mac builds

Mac: Jump through extra hoops for Neon

Mac: Include cross-platform 7zip-bin, not the Linux one

ci: Don't forget to install yarn

Convert `PlayerState` from an interface to a known type

Document more of what's going on

Explain AppImage

Document binary builds

v0.1.0: Get Travis builds (including Linux dist) working!

travis: Attempt to set up basic builds

Move source code to `src/` directory

Set up binary release builds for Linux

Move renderer content to app/ directory

Call the Rust plugin from the renderer process