Feature: support 256 colors

- See https://stackoverflow.com/a/33206814/675577 for example
- At least support bright colors
<img width="181" alt="Screenshot 2019-12-24 at 18 27 33" src="https://user-images.githubusercontent.com/2140450/71591931-1b00a480-2b26-11ea-9cb0-e0cfb36c42ad.png">
