Don't choke on Vim 7.2
Begin transition to rails.vim projections

:Rnavcommand is deprecated.  Projections are the replacement.  Since
it's easy to do per-app projections, I'm only porting over what I'm
guessing are the almost-universal commands.  Note that old-style
singular factories are supported by :Rfabricator, and new-style plural
factories are supported by the built-in :Rfixtures.

I'm not going to yank the existing :Rnavcommand declarations out from
under everyone's feet, but they will need to be removed at some point.