Nix Home Manager: my `.nix` files

Some of my .nix files, significantly inspired by ghedamat/nixfiles and others. Mattia also wrote a nice tutorial to get started.

First steps

The home-manager tool
- Since I want to manage my home directory independently of the system as a whole, I'm using the standalone installation.
Link nixpkgs.
- Say the repo is cloned locally under ~/Code/nixfiles/
- Create a symlink ~/.config/nixpkgs/ to point to ~/Code/nixfiles/nixpkgs
```
ln -s ~/Code/nixfiles/nixpkgs ~/.config
```
Activate the configuration
```
home-manager switch
```
Remember to update, every now and again
```
sudo nix-channel --update
```