* Implement some options
   We need a little more control over the options.  Here are the ones
   I intend to add:
   - Remove HTML
      At the moment, HTML tags in the TODO are automatically made impotent
      by swapping all & characters to "&" and all < characters to
      "<", their HTML symbol codes.  This will probably need to be
      extended to include HTML comments, but we will also need to be
      able to turn this off, with "--nostriphtml" for example.
   - DONE! Formatting options
      These have been moved to a major item, below.
   - DONE! Title
      Something like "--title="
   - DONE! Heading
      Like title, but inserts a H1 tag at the top.  --heading=jhsdjk
   - DONE! Key
      An option like "--showkey" that shows what colours mean.

* DONE! Formatting options
   - DONE! Style sheet inclusion 
      "--cssinsert=" to insert the style info from a given file, and
   - DONE! Style sheet linking
      "--csslink=" to point to an external css file.

* Provide some feedback on completed items
   Ideally, we want some way to show completed items.  Probably just
   make the first word in the heading "DONE!".  Also should work for
   subitems.
   - DONE! Basic highlighting
      Just colors done things green and pending things red
   - Advanced Highlighting
      Instead of having to mark all subitems done, as well as the top
      level item, marking the top level item should mark the subitems
      too.
   - DONE! Auto-off 
      If a stylesheet is provided, this should not provide it's own
      style.
   - DONE! Tag stripping
      An option should be provided for stripping DONE! tags from the
      final html document.

* Allow exclusion of done/pending items
   - DONE! Exclude done items
      Most useful.
   - Exclude pending items
      Not so useful, but worth having

* Write useful docs
   Including proper useage message, help that explains the format of the
   file and a man page.