[PATCH] match other common markdown file extensions

[Chris Burroughs]

On 07/17/2014 09:44 AM, Chris Burroughs wrote:
> -	*.md|*.mkd) exec ./md2html; ;;
> +	*.markdown|*.mdown|*.md|*.mkd) exec ./md2html; ;;

I admit I'm not used to submitting patches via email but noticed that a
similar problem came up in another thread.  Please let me know if I need
to do anything else.