Delete viz/README.md

This file no longer seems accurate, and has been superseded by our readthedocs documentation.

@redsharpbyte: Adding you as approver here, because I think you added the bulk of the info here. If there's anything that's still relevant here, let me know and I'll add it to the readthedocs stuff as part of this PR.

(But also: if anyone thinks this should stick around, let's discuss this!)

Signed-off-by: Hugh Brown (Saint Aardvark the Carpeted) aardvark@saintaardvarkthecarpeted.com