Unable to report version

[raxod502]

When attempting to retrieve the currently installed version of markdown-toc, I receive an error message:

% markdown-toc --version
Usage: markdown-toc [options] <input> 

  input:        The Markdown file to parse for table of contents,
                or "-" to read from stdin.

  -i:           Edit the <input> file directly, injecting the TOC at <!-- toc -->
                (Without this flag, the default is to print the TOC to stdout.)

  --json:       Print the TOC in JSON format

  --append:     Append a string to the end of the TOC

  --bullets:    Bullets to use for items in the generated TOC
                (Supports multiple bullets: --bullets "*" --bullets "-" --bullets "+")
                (Default is "*".)

  --maxdepth:   Use headings whose depth is at most maxdepth
                (Default is 6.)

  --no-firsth1: Include the first h1-level heading in a file

  --no-stripHeadingTags: Do not strip extraneous HTML tags from heading
                         text before slugifying

I think it would be an improvement if the current version number were printed instead.