This adds support for the escape codes generated in rxvt and xterm
format by holding a button and moving the mouse around.

Instead of outdated self-hosted docs, we let the awesome
[docs.rs](https://docs.rs) do the job for us.

Update keys.rs

fix message not appearing

Add escapes to undo styles

Allow colors to be reset to terminal defaults

Fix RawTerminal drop

Termion fmt overhaul

This commit is a major semver bump. Every progra utilizing escape codes generated by Termion is likely broken. The main change is to make each escape has their own type implementing the Display trait.

- Use formatters, mainly Display for escapes.

- Add Truecolor support (`color::Rgb`).

- Put each primitive into distinct modules.

- Add is_tty for checking if some stream is a TTY.

- Add multiple new examples.

Implemented mouse input