zk.zsh -- zettelkästen/wiki/static website helper/generator

* Use plain text files. One file per note/record
* Use CamelCase names, that are friendly with vi editor word
  boundary determination
* You can safely place that notes in subdirectories hierarchy
* Edit and view your notes from their root path (zettelkästen
  root). That way if you press "gf" on "Foo/Bar/Baz" word in
  Vim, then it will open Foo/Bar/Baz file in current window
* Use expand("%:r") function to get current file path relative
  to the root
* Place links to another notes inside square brackets. You can
  highlight them with:
    syntax region zkLink start="\[\S" end="\S]"
    highlight link zkLink String
* Link to the directory's index can be made with [Dir/]
* Use Vim's filename completion (:help compl-filename) to
  complete directories and filenames in them
* fzf (https://github.com/junegunn/fzf) related tools can be
  used to navigate among existing notes
* Ordinary grep, git-jump or similar tools can be used to search
  and quickly open results in the editor

The only thing Vim lacks there is ability to tell who backlinks
to the specified page. zk.zsh can be used to show what pages
backlinks to specified page and what pages are referenced by it:
    $ zk.zsh links some/page
    Another/Page
    SomePage
    $ zk.zsh backs some/page
    [...]
That can be used to make categories and tags on notes. If note
contains a link to category/tag (even an empty file), then it
will be backlinked.

    $ zk.zsh htmls path/to/dir
Will convert all your notes to HTMLs with properly created links
to other pages. It also will include all backlinks in them. Each
directory will also contain index page with links to all
existing pages in current directory and to subdirectories.

If ZK_CACHE environment variable contains path to some
directory, then it will keep caching information for speeding up
the processes in it. Look for CACHE file for more information.