feat(nix): nix and back again

I tried Nix, but it had too many downsides so I removed it.

1. Didn't like that all files are immutable and simple config changes
need a complete rebuild.
2. Setting up a new Mac didn't work as smoothly as promised. Not worth
the effort.
3. It sucked a lot to always have to type in the password twice on each
darwin-rebuild
4. It solves problems I never had.

.config/git/ignore

@@ -0,0 +1,12 @@
+*.lnk
+*.pyc
+*.pyo
+*.session
+*.sw[nop]
+.BridgeSort
+.DS_Store
+._*
+.agignore
+.bundle/
+m~
+tags