move all expressions to nix/; include modularized home-manager config

nix/home-manager/programs/emacs.nix

@@ -0,0 +1,24 @@
+{ pkgs,
+...
+}:
+
+{
+  programs.emacs = {
+    enable = true;
+    extraPackages = epkgs: (with epkgs; [
+      nix-mode
+      magit          # ; Integrate git <C-x g>
+      zerodark-theme # ; Nicolas' theme
+      undo-tree      # ; <C-x u> to show the undo tree
+      # zoom-frm       # ; increase/decrease font size for all buffers %lt;C-x C-+>
+    ]) ++ (with epkgs.melpaPackages; [
+      evil
+    ]) ++ (with epkgs.elpaPackages; [
+      auctex         # ; LaTeX mode
+      beacon         # ; highlight my cursor when scrolling
+      nameless       # ; hide current package name everywhere in elisp code
+    ]) ++ (with pkgs; [
+      pkgs.notmuch   # From main packages set
+    ]);
+  };
+}