Add config for mackup

- ignore apps whose config files are in the `dotfiles` repo
  (see: https://gitlab.webartifex.biz/alexander/dotfiles)
- include various (config) files that should not be public:
  + Cisco's AnyConnect
  + history files for `bash`, `less`, `python`, `psql`, `tig`, and `zsh`
  + Nautilus' bookmarks
  + SSH config & known hosts

README.md

@@ -41,3 +41,10 @@ Additionally, two `virtualenv`s, "interactive" and "utils", are also created:
  - "utils" hosts globally available utilities.
 
 Use `pyenv local ...` to specify a particular Python binary for a project.
+
+
+### Non-public Dotfiles
+
+After setting up the Python environments (i.e., the "utils"),
+    running `mackup restore` symlinks further dotfiles into `~/`.
+This only works for this project's maintainer.