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.