Contributor Guide, Appendix, and link BC

Main feedback I'd like here is how people feel about this method of maintaining backward-compatibility with our links. What I've done:
 * Leave behind "gravestones" for old pages, with links to the new location.
 * Add old pages to the "appendix/moved" toctree so they don't clutter the main toctree

I despise dead links, but I don't see a cleaner way that sphinx allows. If anyone has insights here I'd love to hear them.