Fix the documentation link and format it better.

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Instead of outdated self-hosted docs, we let the awesome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