- Diction does not really interpret "#" as a comment character in its
  rules file -- we currently just hope it never matches.

- Remove comments for `gosh' input, just as for LaTeX input.

- Parse LaTeX's \include directives

- A better algorithm for detecting double words

- Add an option for showing the error message separate from the text

- Should we return an error code when we found problems?

- Add a method for disabling warnings on a per-sentence basis inside
  the document.

- Allow disabling warnings.  Maybe introduce warning levels.