RTF Support

Over the years, I have made many comments and answered many questions about MultiMarkdown and RTF. I won't rehash everything, but will use this to store a concise version in a single place.

1. RTF is a terrible format. With the rise of OpenOffice and Libre Office, I don't believe there is a place for RTF anymore.

2. I understand that some people, by virtue of their employment and other external constraints are required to use RTF. To you -- my sympathies.

3. MultiMarkdown does not officially support RTF.

4. Over the years there have been a few ways to partially support RTF:

* MMD v2 used XSLT to convert HTML into RTF.  It supported some, but not all, MMD features.

* MMD 4 and 5 had partial support for RTF as an output format -- I started it with the hopes of getting other people to help.  No one did.  It was never finished.

* OS X provides the `textutil` program that converts HTML to RTF (among other things).  Depending on your needs, this may or may not be satisfactory.  Complex features (e.g. tables, footnotes, etc.) may not work as expected.

1. If you must use RTF, the officially recommended way to do it and get the best results is to convert text to an OpenDocument file, and then use OpenOffice or Libre Office to convert that into RTF. In my tests, this gives a much better result than any other method.

2. I have had a standing offer for years to help if anyone wants to tackle the challenge of providing better direct conversion of MMD to RTF. To date, no one has taken me up on this. It still stands.