Simplified emacs setup and made it default

hosts/darwin/default.nix

@@ -75,7 +75,19 @@ in
   environment.systemPackages =
     with pkgs;
     [
-      emacs-unstable
+    # Emacs with automatic package management from overlay
+        (emacsWithPackagesFromUsePackage {
+          config = ../config/emacs/emacs.el;
+          defaultInitFile = true;
+          package = emacs-unstable;
+          alwaysEnsure = true;
+          extraEmacsPackages = epkgs: with epkgs; [
+            magit
+            company
+            nix-mode
+            use-package
+          ];
+        })
     ]
     ++ (import ../../modules/shared/packages.nix { inherit pkgs; })