Make mode-line look non-awful

[PythonNut]

Principles that I would like to emphasize in the redesign:

1. Minimal design (e.g. minor modes can go in a minions menu),
2. Retains evil-mode colors,
3. Works well in both terminal and GUI (but GUI may be more appealing),
4. Nearly zero startup overhead,
5. Avoid blocking the main thread at all costs.

[PythonNut]

https://github.com/seagle0128/doom-modeline looks nice.