Thanks @shamilbi

Thanks to:
 - Dmitry Vyukov @dvyukov for the idea
 - Daniel Vetter @danvet for the knowledge

Refers to #32

That makes print_checklist() much better.

Thanks to @Mic92

Refers to #27

Refers to #27

Allows installation via nix from the repository itself
on NixOS and other Linux distribution that have Nix (i.e. Archlinux/Debian).

```
$ nix-build
$ ./result/bin/kconfig-hardened-check
$ nix-env -f . -i
```

It also provides an development environment for `nix-shell` with setuptools and
python in path

```
$ nix-shell
```

Thanks to @Mic92 for the proof-of-concept

Refers to #26