Remove old wiki

[schumannd]

I was just updating some missing documentation in the wiki (behavior of RNFS.fs.df() on android vs. iOS) when I realized I accidentally had the old wiki open. This got me thinking whether this might happen to other contributors and whether it is possible to remove the old wiki. If possible, I think it would be a good Idea to avoid having two diverged versions of it.

[Traviskn]

Unfortunately I do not have administrative access over the old repo, so I don't think that I could remove the old wiki. Since it is a wiki though, we might be able to add warning messages to the top of each page directing readers to go to the new wiki for the latest documentation